Just curious really.... A friend recently purchased a used android phone from ebay. The person who sold it to him accidentally left their SIM card (or a SIM card) in it when they sent it to him. Nothing nefarious. He sent the SIM back without even contacting him about it first or trying to see if it was a working SIM. Now, I know that if it was an active SIM the person could easily just cut service to the card. But he asked me and got me wondering, if he signed in with his google account on that phone, what would happen regarding the SIM? Would it be his phone with his apps and gmail, etc but with a different number? That is my guess...but if so, what would happen with text messages, google voice, etc? Thanks!