How can I get my straighttalk plan to replace the previous owner's Tmobile data plan?

[AC Question]

I just got an unlocked Samsung galaxy s4 and ordered and received sim cards from Stratightalk that use Tracphone. Even tho Straighttalk helped me set up the apn settings (twice) i still don't have working data. I can use the phone but no Internet unless i'm on WI FI. The Tmobile tone still sings when I send a message and it says "sent from my tmobile LTE". what should I do?