Truworths harassment

I'm a disgusted with truworths. I am being harassed daily to pay an account where they can not locate the payment for whatever reason even after sending them proof that the payment was made on time. They agents only say they will escalate but that doesn't help If it's not resolved. Truworths needs to locate this payment and better pray this doesn't effect my credit score negatively. Further more I would like someone to contact me with a solution and compensation for this BS.