MTN - Not allocating payments and erroneously handing accounts over as in default with Credit Bereaus

I paid my account in August 2020, but to my dismay see that they've registered my account as in default. I sent through the proof of payment to *** to query this on 8 May 2021 and they referred me to ***. I sent through the proof of payment to *** on 10 May 2021 and again on 12 May 2021 and was given Trouble Ticket#: *** to allocate the missing payment. I followed up on 20 May 2021, on 26 May 2021 they responded asking which banking details I had used (this info was also on the mail train but regardless I sent it again) and I rep**** on the same day with banking details used. I have since followed up on 1 June 2021, 10 June 2021, 16 June 2021, 1 July 2021, 16 July 2021, 27 July 2021 and 3 August 2021 and have received no response on any of my follow-ups.