Contract cxlled but MTN keeps on taking money

In May I cancelled my MTN contract after 18 years with MTN and ported my number to Telkom. I was still invoiced in June, and I complained to their customercare@mtn email address, and received no response, nothing! Now in July I am receiving more invoices and billing from MTN for this cancelled contract, and I went into the Nicolway branch of MTN, but was told theat the account is still active on the system. So I have emailed the customer care line again but still no response. I have demanded that they cease debiting my account, and refund my the money they have taken *******ly, but I wonder if they will ever stop debiting me, I see the MTN CEO has even resigned there! The MTN brand has been irreparably damaged in my eyes...