TERMINATING OF MTN CONTRACT - NO COMMUNICATION FROM MTN

Communication from MTN with initial signing up a 2 year contract was immaculate...now terminating the contract after 2 years .....NO COMMUNICATION whatsoever !!!!!!!!! On 19 March 2020 I've notified via email that my contract completed full term by 30th and that I want to terminate because of relocating to another country.(By the way.. I've received for past 3 months emails and sms's without end reminding and prompting me that I'm due for upgrade)I received an automatic reply email with enquiry ref number with a promise of "we will make contact within 8hrs".... on 30 March 2020 I've gone on their Facebook page as well as Messenger with the same story.....the promise there is "reply within an hour" needless to say NO REPLY!!!!!!!! ........today 1 April 2020 and MTN will shortly take my money for yet another month for a service I no longer have use of. How on earth do I get to communicate with this company????????????????Do I have the right to notify my Bank to stop debit order payment or does MTN have the authority to abuse my situation????