u/AdMental940

Last week, I accidentally shipped the wrong parcel at a drop off point. I had 2 parcels to ship and accidentally shipped parcel B to buyer A. I contacted both buyers, and shipped parcel A to buyer A at the post office at my own expense last Tuesday. So now buyer A has both parcels, they contacted me on wednesday asking me to what to do with parcel B, I asked if they would ship it for me and sent them the QR code for it. They said they would ship on Thursday, I told them great as the deadline was Friday. However I didn’t trust them, so requested a shipping extension with buyer B. It is now Monday and buyer A has not shipped parcel B and is not responding to messages.
Do I just cancel the order with B or see if i can contact A??