The pre-paid folder doesn't allow me to make payments more than once per day, and I have a client that payed R50 this morning, and again just now. HELP!

Yes, it is a basic security feature, similar to Standard Bank's internet banking, that we don't allow the same amount payment on the same day, from/to the same customer, to avoid duplicates on the system and enhance data integrity and minimize fraud.
For instance, you should be able to load R51, since that is a different amount, or R49, or even R49.99
The best way to handle this would be to restrict the customer, to not accept payment of the same amount multiple times on the same day, so that confusion is eliminated all the way down from the top to the bottom, otherwise if you do 2 submits or a page refresh, it could take 2 payments, when the customer only did one, or the customer could claim he did more payments when he did less, etc.
Please let me know if the above is acceptable to you, or whether you want to circumvent this security feature. My advice would be not to circumvent it, since it is also there for your protection.