Question for lawyer regarding bank account and Verizon going into it?

My son, has his own verizon wireless account, and for some reason Verizon decided to go into my bank account and take money out to pay for his bill? I dont even live with my son, or have i ever gave anyone authorization to go into my bank account. They have simply just broke the law and on the phone could not explain what happened and sounded scared when I pressed them about it. If i chose to get a lawyer what would be the amount of money i would get if i sued them?