Account payment issue

I paid my account online on their provided link with my card on the 24th May. I sent them a screenshot of the transaction. After 8 days they still did not receive the payment and continue to phone me and threatened that they will list me as bad payer. After numourous phone calls and emails, my bank confirmed the payment was made, the problem is with the merchant , they need to bank on their side , then only the payment will reflect on their system, if they fail to bank within 14 days, then the payment will be returned to my bank. They demand i send them my bank statement to prove i paid, but they cant understand that the payment wont reflect on my statement as they have not banked yet. So this in continuing up and down just to get them to understand its THEIR system thats the issue, not the account holder that made the payment. They need to self investigate instead of phoning me 5 times a day for a payment. Terrible *********** company!!!!!

This is also not the first month that this happens with their online payment link!