I'm truly wondering if anyone can ask this crazy question of what I want to do. Here it goes:

My GF and I have Sprint. She is on her own plan, I have a family plan with my mother that I pay. My mother wants another phone added. Is there a way to take my number to ATT And have my mothers line become the main line so I dont have to pay a fee to end my contact and add a second line to that? Then later take my GF's number and add it to my new ATT plan (both would be Iphones)