Incorrect or ******* Contract Closing Process

I took 2 cell phone contracts in Jan 2016 with phone number ********** & ********** from MTN Benmore shop. I have visited them during Nov 2017 to advise them to close the contracts by 13th Jan 2018. However they have mentioned that for contract closure I have to call 808 and closures are not done in the store.

Subsequently I have called 808 and spoke to the consultant to terminate the contract by 13th Jan 2018(upon completion of 24 months) and change the number to pre-paid. But they have told me I need to contact them the day after the expiry which is 14th Jan 2018. When I called on 14th Jan the call center was not opened and I need to call them on Monday (15th Jan).

So I have called again on 15th morning and one of the consultant assisted me to close the contract (Ref. ********** 15). I have specifically asked if I would be liable for any charges and he said NO. However on 21st Jan I have received the invoices which was unexpected. I have sent emails to customercare as I was no longer able to reach their contracts department.

Even after providing all the necessary proofs that they have collected the money for 24 months they still deducted this month again(Jan 2018)

Questions/concerns: 1) If they are not available on all days (looks like they work from Monday - Friday only) why would they ask me to call a day after the contract closure? 2) If I spoke to them 30 days in advance why would I need to call them only a day after completion of 24 months 3) Though I have proved that I have paid 24 moths they still insist that they haven't collected which shows they have very poor understanding of handling queries