will a att sims card work for a virgin mobil phone?

No phone locked with virgin network wont accept cingular or any other GSM sim until you unlock the phone from virgin network .You can easily unlock the phone using sites like TheUnlockArena.com here they are rendering network unlock code for all mobile models at reliable cost .You first check that whether the code is available for your mobile model ,country and network provider .If yes then pay for it and unlock your phone ...