MTN No Service and suspected *****ulent activities with my information!

I had a month to month data contract that I cancelled on 26 April 2024. I returned my router at the MTN in Shelley Centre to NONTU and received a one page document of cancellation. I kept on receiving bills. I reached out to Customer Service, have phoned and went in personally to get this sorted and confirmation that my contract have been cancelled and account closed, NOTHING happens apart from the fact that I keep on receiving emails with amounts due and welcome emails to my new plan! I have not got a new plan so my information is used to facilitate other peoples applications. I have contacted the ***** section, but no joy. Retention department, no joy! How difficult is it to cancel a contract? I would NEVER refer anyone to MTN and especially not the branch at Shelly Centre in KZN. Be aware of them.