MTN clueless - non allocation of payment made by me 7 months ago

I am an MTN contract customer. My son paid my March 2021 monthly bill of R438.42 on 10 April. MTN have still not allocated this payment. I have contacted the MTN call centre on numerous occasions, sent MTN e-mails and facebook messages regarding this non allocation, but to no avail- this amount still remains unallocated 7 months later. MTN have acknowledged the proof of payment that I sent through months ago, but keep advising that the banking department has not allocated the payment. MTN have suspended my service on a number of occasions, believing my account to be in arrears; I have had to phone the call centre to reconnect me to the network. Today I received an SMS from MTN threatening to cut me off again if I do not make payment of this "arrear amount' and t9hat non-payment will affect my credit rating. I am absolutely disgusted by the service of MTN and that they cannot resolve a simple payment allocation. My billing profile is BA***. This payment allocation better be resolved by tomorrow (9 November 2021) or I will take out my next contract with Vodacom (I am currently due for an upgrade)