Do not want to allocate payment to my account.

this does not even deserve a star. I placed a lay-by order on the 28/03/2023 and made a R350 deposit using their online portal. On the 28/04/2023 i used the same portal to make payment of R1600 and referenced my sales order number and they say that it does not reflect. I sent them my bank statement which shows the payment but they insist on a POP which i do not have because i did not pay via EFT but via the online payment system available on their website. i sent them bank statement and even told them they can call my bank to confirm my payment but they refuse to do so. They are not willing to help in any way to allocate the payment.