Charging and Billing an account for no reason

I have had a personal contract with MTN which has expired and terminated three years ago Cell number ********** 933 . since the last two months MTN is charging me by Debit Order to my account which they have the details of from the past. they refuse to cancel this account they say it is now belongs to a company ? the account has been hacked, or someone has using my ID which is *****.

They asked for for a proof that the account has been terminated? they are to provide me with what right do they have to charge my bank account for a contact and a cell phone number which has not been used for three years. and confirmation has been sent to them three years ago to terminate the contact they are Useless.