Ya sure you can easily unlock your sidekick mobile from t-mobile provider then freely use it with AT&T or any other GSM sim ..You can easily unlock your phone through online providers like TheUnlockSpot.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 the phone then freely use it with any GSM sim ..
