is my z550 done?

[jjbadd]

to make a long story short, i was given an unlock code by t mobile to unlock my Suncom branded z550, however it was the wrong code and it failed 5 times and will let me type in a code now, but says "not allowed" now. Sony told me it was forever locked to Suncom now which i dont beleive. Suncom dont exist anymore, so how do i begin to fix this situation? i dont mind reading if someone will let me know if its fixable and what do i need to read? i am new but not totally dumb:)! thanks 4 helping. jj

**im sorry, i am with t mobile now and i want to use the tmobile SIM. this phone will only accept a suncom at the moment. i may not have been clear.