Insist that the postal code is invalid, can't proceed- It is the correct code with 4 digits

My acc no is : ***. I complained about unsuccessful placing an order online several times. I tried it from the app, online, computer and several cellphones, NO SUCCESS. Keep on getting a message postal code is invalid, can't use another code because it is the correct code- ***amas 8870. I also get a message it must be more digits. It is on the country South Africa. Pargo won't choose the town if I click on choose this point. If I can get to the last step of the process, it return to this step after I pushed the button, it doesn't gave me the order no. I gave you only today to finally correct this issue, it is coming a long way already, and it must be on your side.