Legal Question in Landlord & Tenant Law in Georgia

No, and you should immediately complain to the Georgia Public Service Commission.

The answer may very well be yes, and you left out important details (perhaps intentionally). I used to handle these issues for a large utility. Utilities, unlike other creditors, are forced to do business with people and they are diligent about going after adults who use and benefit from their service at one location, then try to get it at another location perhaps in someone else's name. Generally, they are allowed to do it. The information you left out of the story is whether your boyfriend actually lived in the other house and got the benefit of the service. That is what the utility asked you, right? Not his "mailing address" and not what the lease says? If so, now he is trying to get the benefit of their service at the new address while the old bill has not been paid. Who is on the lease is not the issue - that is your contract with the landlord, not the utility. You've already let them know he is going to live there - changing the name on a lease does not change that. If he did not live at the old address (again, they would have raised this question), he can give them evidence of where he lived. As far as your personal liability, no, you are not liable for the old bill and it will not or should not follow you. That does not mean they have to provide your boyfriend with new service. You can complain to the PSC, or the easiest solution is to tell the sister to pay her bill.

If it is only the gas company, you are fortunate. A large power company does the same thing if they find out.