I'm under contract with T-Mobile but my 1.5 yr-old phone broke is no longer under warranty. T-Mobile either wants a 2-yr contract extension or purchase a new phone for many $$.

All I want is a functioning phone -- if I buy a used unlocked T-Mobile phone from E-bay and put in my SIM card from the current phone, will that result in a funtioning phone ?

Or, do I need to activate it ... ?

Thank you for the help/advice!

Regards,
Mark