u/ZoneyMiles

In Season 5 Episode 6: Artificial Emotional Intelligence, Bighead asks Fiona (the AI bot) a maths question, she answers. He then double checks by asking... Siri!

Obviously just a writing error but this implies that Apple also exists in their universe, and even though Bighead worked at Hooli, he decided to buy an iPhone after leaving.

Edit: on closer inspection, it is definitely a Hooli phone. As Richard also uses one shortly after and the form factor is not an iPhone.

This implies that Hooli phones don't have an assistant and are integrated with Siri instead.

I'm gonna have to go back in episodes now to figure out if a Hooli assistant is ever mentioned or used.