Problems making calls

[Guest gemuuu]

Not sure how much help I will get considering the phone is now pretty old but anyway...

I own the T-Mobile version of the HTC Hero and I paid for an unlock code to use other sim cards. Since doing this I now can't place calls or send/receive texts on any sim card, even T-Mobile. It says I have signal (including 3g) but I just can't seem to use it. I've tried installing a custom ROM and that hasn't helped either. Other than that the phone works fine and I can browse the internet on WiFi. Any ideas? Would like to have it available as a spare phone.

Thanks