Mtn ******* debit

I had a 36 home wifi with mtn and the contract was ending 26 April 2025 and a month before on the 26 March I sent mtn customer care an email notifying them I won't renew my contract beyond the 3years.now they are debiting my account and I'm reversing it as I'm not using their router or Sim card now what service are they charging me for.