Sending your account has not been paid -emails!!

I was billed R10 in January for a sale made on bid or buy. Unfortunately the bank sent he debit order back - On 3rd February I paid R14.50 which included an additional fee. This HAAS gone off my account as it was a manual EFT. Now I get sent an email a MONTH later saying I owe them money. I have proof of payment so PLEASE sort your won accounts system out - I sorted mine out _ you sort ot yours! And please do not re submit _ get your accounts up to date!!!