UNAUTHORISED CHARGES.

I had a home router contract that was not in use because the network in the area is bad. The contract ended in November ‘24. In October I specifically called in to say my contract is ending, I don’t want upgrades and I don’t want to go into prepaid as I am not using the router. Beginning on December, I get a charge on my bank account from them. I call in and they said my account is now on prepaid. WHY?! I SPECIFICALLY SAID I DONT WANT TO BE ON PREPAID. I SAID I DONT NEED YOUR SERVICES ANYMORE! SO WHY?!