PAYING FOR CANCELLED ACCOUNT - 8 MONTHS LATER!

We moved out of South Africa in December 2017, upon which I cancelled my contract. I had to pay a settlement fee of R3173 because my contract hasn't expired, which was sent to their retentions department in December according to their instructions. In January I noticed that I was STILL being billed over R500 a month for a service that I cancelled and don't use. I emailed them about it. Today, I checked my South African account and I see that they are STILL billing me every month for this account. Apart from the settlement fee, this means I have paid another R3925 for service that I don't get. They are simply not responding to my emails.