TeleCircuit Changed my service without my authorization. Kept calling. My who is sick answered, but the account was in my name Duluth Georgia

Dallas TeleCircuit kept calling me on several occasions.  I was never inside to take the call.  The calls were from a Robert Miller (their agent)  Finally on October 6 my wife who is sick and is now in the hospital said OK. Her name was not on the account. I called back and told them not to change it, but they said that they already changed it and that if I wanted it back with AT&T that I had to call them.  I called them and told them to change it back, but I had to call back several times to get it changed.  It is changed now.

I received a bill from them soon after for $46.71. This bill stated that the Billing period ended 10/6/2017.

This was strange as that was the day my service was changed.

I did not pay this bill. (I told them when I called back that I was not going to pay them anything)

Recently, about 10/27) I received another bill for $94.42. This said the billing period ended 10/20/2017.

I MIght accept an arbitration amount.  But I really don't want to pay them anthing because of all the trouble they put me through.

If I just don't pay them anything, what kind of problem can they cause me?