Fitness Connection Entered into a contract with a minor Spring Texas

My son was given a membership to this gym as a 16yr old. It was a Christmas present from his older sister. My son never had time to use the membership so he asked his sister to cancel the membership. She tried but they continued taking money out of her checking account. She sent letters to cooperate and made many phones calls but could not get them to stop taking money. She had to close her checking account. 

Now its 3 yrs later and fitness connection hired a collection agency to go after my son. They have no social security number, only his name. They are telling him they are going to sue him and report hom to the credit bureau and ruin his credit if he doesn't pay. Mind you they don't have his SS number. He was so scared it would happen that he paid what they were asking. What kind of company claims to enter into  a binding business contract with a minor without parental consent. Stay away from this company. They will go to the end of the earth to see to they get paid, even after you cancel their services.