I have an invalid SIM error. What can I do?

[iMore Question]

hy gud day i ave a iphone thats not activation keep say sim not valid an am putin the tmobile sim in why

 

[kch50428]

Sounds like it may be locked to another GSM provider.

 

[Jaguarr40]

Where did you buy it? If from a carrier ask them to check if it is locked and if so will they unlock it. Then you can use the sim card you have.