Unlocking a phone

 I got a new phone so I gave my old phone to a family member. They transferred their SafeLink Wireless account onto the old phone, but they are not able to send or receive texts. They contacted the support for SafeLink Wireless and were told that the phone may have restrictions and to contact AT&T about getting it unlocked. I tried doing it through the website, but I got an email that said the phone couldn't be unlocked because it is active on another AT&T customer's account. I tried to contact the GoPhone support phone number but there is no way to get help for this problem there. Please help!