My Experience/Guide To Setting Up Tello as an Immigrant/Expat (iPhone, US to Germany, From Within the US)
Actually not a fan of the word expat but that's what will help it come up in search, so.
Throughout my move to Germany I've decided to write down my experiences, good and bad, to help others. I am moving in a little over a week so I am still stateside--I CANNOT give any advice for activating abroad, but there are multiple threads on the subject. It's way easier to do in the US so for my fellow Americans looking to live abroad, add this to your "do before you leave" list.
BEFORE YOU DO ANYTHING:
Make sure your phone is unlocked. When in doubt, call your carrier and ask. If you have an iPhone, you can also go to Settings > General > About > scroll down to Carrier Lock. If it says "No SIM restrictions", you should be good. But again, your carrier is the best source of truth on that. If your phone is locked, you will not be able to add a new number or switch until it is unlocked.
Make sure your phone is compatible. Tello as a nifty little tool so you can make sure your phone is able to run the network anyway, which would be a handy thing to know before giving them your credit card information. As their instructions say, "Dial *#06# on your phone and you'll receive your phone's IMEI code" OR on iPhone you can go to Settings > General > About and scroll down to see the IMEI.
PHASE 1: GETTING THE ESIM
STEP 1: Sign up for Tello. Was super easy. As I was starting in the US I picked the unlimited plan, which is still only $25 a month. I used my legal U.S. address for the account/for tax and area code purposes. I got access to my dashboard immediately as well as an email welcoming me to the platform.
STEP 2: eSIM activation. I have an iPhone 14 which is eSIM only but supports dual eSIM. With the QR code open on my laptop, I scanned with my phone camera and followed the instructions. It was very simple and took about 2 minutes to activate.
STEP 3: dual eSIM configuration. My iPhone prompted me to label my new secondary line as well as my original (Verizon) line. I was able to choose my default voice and data line, which I left on my primary for the time being. Don't worry about having the second number--you can replace it with your old number later.
STEP 4: Testing. I switched off my primary line and texted my sister from my new number, and asked her to test out texting/calling me. Worked perfectly. I live in a bit of a dead zone so I wouldn't say it was lightning speed internet browsing, but it was the exact same with my old carrier (Verizon). Call quality was just fine. Also, this little test helped satisfy Tello's "you have to use the line in the US before activating international roaming" requirement (although that was tricky, more info on that below).
STEP 5: The app. I guess it's not a necessity but I downloaded the My Tello app for easy access to settings. Have them send you a one time SMS code to log in (you have to initiate it, the login doesn't do it automatically).
PHASE 2: INTERNATIONAL ROAMING
This was a little tricky. I knew I needed Wifi Calling at least initially while abroad so I turned it on during carrier setup, using my current US address as the E911 address. However, this turned out to be a problem when trying to activate roaming. So this is what I ultimately had to do to get it set up--again, while in the US.
STEP 1: Disable Wifi calling (or just don't set it up right away).
STEP 2: Turn off the primary line to force your phone to ping T-Mobile towers on the Tello plan.
STEP 3: Add Pay As You Go credits, minimum $20 plus tax.
STEP 4: Use your phone. Make calls/texts, browse the internet. It may take up to 48hrs for this activity to show up in your account.
STEP 5: Correct settings on your phone's side. For iPhone, this is under Settings > Cellular > your Tello number. Scroll down and ensure the network selection is Tello, Wifi Calling is off, Voice & Data is LTE, and Data Roaming is on.
STEP 6: If all of this doesn't work, do the ol' refresh. Turn your phone off and on. And finally--what actually worked for me at the very end of all of this! Reset the cell network settings. On iPhone, go to Settings > Cellular > your Tello number > Cellular Data Network. There should be an APN with the name "wholesale". Scroll down and hit "Reset Settings". Then go back to your Tello Dashboard and try again. This is what finally allowed me to turn on International Roaming on the Tello account side. I was definitely pinging US towers but I think it just wasn't getting through until I refreshed things.
NOTE: You will still definitely want Wifi Calling/a travel eSIM when you travel abroad because Tello's international roaming prices are insane ($50/GB). It's just a good thing to have as an option for emergencies. You can enable or re-enable this once you've turned on International Roaming.
PHASE 3: PORTING YOUR OLD NUMBER
If you don't care to keep your old number then skip this. You can just cancel your old plan on your time.
STEP 1: Verify eligibility. The first thing you'll need is to find out if you can even port your old number. Under your Tello Dashboard, go to Number Transfer and check your old number. If it is possible to transfer the number, they will give you a bunch of fields to enter your account information into (account #, porting PIN, etc).
STEP 2: Get information/the breakup convo. Getting this information right is critical to ensure the port works (I think of it as like doing a bank transfer--make sure the names and numbers are 100% accurate to the letter). For the best accuracy, you will want to go to your old carrier and request this information. Awkward. But they have to give it to you. If you have Verizon, you can actually get the "Number Transfer PIN" generated from your Verizon account. Less awkward.
STEP 3: Submit the information and start the port. Your old number will replace the new number. Note that if you only had a single line on your old phone plan, this port will effectively cancel your previous phone plan so you will be billed for any outstanding fees/payments if your phone isn't paid off. (This is another reason you want to talk to your old carrier beforehand--if you are in a contract, you need to know how much it will cost to break it. If you have a promo plan, you need to know how much is left to be paid off.) For me, the transfer was done in literally 3 minutes.
STEP 4: Reboot and set your new voicemail. You'll get an email from Tello once the port is complete with instructions, which basically boil down to this. Check your Cellular Settings first to make sure the new number is in there (note, your old eSIM will probably stick around, so it'll look like you have two eSIMs with the same number, but the old one will be inactive). Once you've confirmed your old number has been brought over, restart your phone. I relabeled my Tello eSIM as primary and was able to set up my voicemail from the Phone app, but the Tello email will contain alternate instructions to do that if you don't have an iPhone.
STEP 5: Final test and delete the old eSIM. Make one last round of calls and texts. Browse the net. Make sure you've turned wifi off so you're actually testing the cellular data. Once you've confirmed your Tello eSIM is working, you can safely delete the old one. Hit the road, Jack, and dontcha come back no more no more NO MORE no more...
STEP 6: Paying your final bill. If you're an ex-Verizon customer, you should still be able to log in to your My Verizon account. I literally just ported my number this morning and while it's showing me what my charges (which is mainly a small device payoff) will be it's not letting me actually pay. I'm guessing it will show up on my next billing cycle. I have auto pay enabled anyway so I'm sure they'll come back and get what they want.
I hope this helps somebody. This is my first time doing this--I got this number 12 years ago when I signed up on my family's Verizon plan right before I went to college. Funny enough, we all eventually broke off in different carrier directions and I was the last Verizon customer, mainly out of laziness and the fact that they were paying my phone off. So far Tello has been very easy to use and the service is just fine considering the area I live in which is notorious for having bad service anyway. It's mainly music streaming and internet browsing which are slow. Texts are ok and calls are clear. Outside of my particularly touchy neighborhood, all service has been great. I'm not planning on using it much while overseas but it'll be a nice thing to have when I'm visiting home. $25/mo for unlimited with 50GB of high speed data per month is a pretty dang good deal IMO.
Danke und viel Glück ;)