Payment from FNB to Standard Bank not reflecting 5days later

A client made a payment to our account on 31 October 2021. Today is the 4th of November and the funds are still not reflecting. Trying to communicate with FNB on this is just not getting us anywhere. I understand that this is now a common problem with FNB as many people are complaining about this. So how do we fix this if FNB is failing to assist????