I had a contract with MTN that i was paying 3years

I had a contract with MTN that i was paying 3years. On the 16/09/2025 was the last day of the contract.I phoned them 30days to give them month of cancelliation.I called on the 15/08/2025 since 16 Saturday .They said 15 is early cancelliation and there will be penalties, and still Monday of 18/08/2025 will be a late cancellation.I complained on emails and eventually i got scheduled for 18 with no penalties.They deducted their normal instalment of R768,64 on the 01/09/2025 which was supposed to be their last instalment.I received email last week i still owe an amount of R809 now. A lady i spoke to last time said he doesnt know how they ended up to R809.