BIS Account from a Used Phone

[TMD17]

Hey I just purchased a used phone off of ebay. I'm wondering if I run into the BIS account already in use by the previous owner, will I still be able to activate it? (I can't deactivate it) If not, should I return the phone if this situation comes up?

[AZBBFAN]

Tmob will be able to take care of it for you. call them after you get the phone if you have problems