I think this kind of thing will happen anywhere. Sales people earn commission they have to make sales. When people come in with problems they are going to try to upsell them This was probably, actually, a deal as others have mentioned. Hopefully the tech issue was resolved with the new phone. Since he signed the paperwork it is legally binding. You can try to see if Verizon will let him back out of it but they don't have too.

If you grandfather has problems in high pressure sales environments--many people do, elderly and non elderly, go with him to the store. Or help him solve his tech issues yourself when you can. This is what I do for my family. For me, it's usually easy to fix and keeps them from feelings pressured and not fully understanding what they are signing.