Cell C doesn't find my Payfast payment

On 7 January 2025 I got a sms that states that my Cell C account wasn't paid for December. I Iooked on my bank statements and it does show that I paid my account on the 19th of December via PayPast on their app. I called Cell C, but as usual, they couldn't help me at all. Not long after that, I got a email from the Cell C collection people stating my account is overdue and I need to pay the R485. ***. I always pay via payfast, but now suddenly they don't pick it up. I don't have time to sot sort out their **** Payfast System. I need this account to be sorted out and corrected ASAP.