Credit Still Owed

I upgraded online last year due to Covid. I was debited an extra R1400 for one month. When I phoned them they admitted fault and made sure the amount debited in future months was correct. I asked if this amount could be offset against my account as a credit. To date, and many calls and escalated queries later, I have yet to recieve that amount, either as a credit or a refund. I called today to follow up on my last reference number and was told that not only do they not have any queries on my account, but they don't have any record of me past March 2021. Covid has hit everyone hard financially, and I cannot afford to give R1400 away for nothing.