How to change numbers on a used iPhone?

I got this used iPhone but their phone number is still connected to the phone? I'm pretty sure it's deactivated though because I haven't received any texts or calls from anyone. I was just wondering how I could put MY phone number on the phone instead of the other one. Plus it is a VERIZON iPhone if that helps.

Provided that the ESN # (basically the unique identifier number of the phone sort of like a serial number) on the phone is CLEAN (ie not reported lost or stolen by the owner and all the bills were paid and there's no outstanding balance), then you would just call Verizon's customer service to do it.

Go to Verizon, and they will give you a different SIM card for it, or do something else to change the number.