IPhone 4 Help Needed?

Firstly, i bought my IPhone 4 Sim Free from the Apple Store.



I initially had a PAYG T-Mobile sim card and my phone worked fine. I swapped it around with another for a few weeks and then back to my T-Mobile Sim, again it worked fine. Upon swapping my sim once again i found that i'm now unable to make calls, I can however receive calls and send and receive txts. I have tried the sim in another phone and it works perfectly. I have also checked my T-Mobile sim in my iphone and that works fine too. I have tried restoring the phone from a backup, this doesnt help. Any Ideas?IPhone 4 Help Needed?
Many are complaining about this. It is because T Mobile got themselves in trouble with fraud and was sued. They are forcing you to merge with ATT. It is just pending FCC approval. They want everyone to buy new phones so they can make money and they know full well that the phone wont work. Please do not sign a new contract or you will be hit with early termination fees.