Disappointed

I paid my account via EFT from pep website ozow on the 4th of January I keep getting messages that I didn't pay, I sent a screenshot of the sms and my bank statement to show when I paid the account and the time. I was on WhatsApp chat and they said they can't help me they want proof of payment and the account number o used to pay. How do I know the account number that they used for Ozow, can't they check my statement and amount against the date? I would know what account is linked to their internet payment, how's that possible? Can't they check the date and time against the amount from my statement. Poor service I'm disappointed and I think paying up at the store and closing the account will do.