RCS not doing their Job!!!!

My Husband settled his Makro account in February, but to date they have not updated their systems with the settlement that was paid! Thus resulting in constant harasment sms's and phone calls asking him to pay his account! Proof of Payment with the reference number which is his Makro account number has been emailed to them a million time and each time someone different assist or no feedback at all! The last time someone called him the lady said she can see the payment but the finance department has not updated their system yet! Now they phoned him again today requesting payment! Absolutely PATHETIC!!!!!!!!!! How did they pick up the monthly payments each month, but cannot see the big settlement amount that was paid??? Again PATHETIC!!!!!!!! How can this be sorted???