Refusal to pay over funds

Good day.

I recently hosted an event and was selling food and beverages. I have a Vodacom speed point that I use for accepting card payments. All went well and for some reason one of the transactions/amounts is being disputed. Nedbank is refusing to pay over the amount, which is a legitimate purchase at the event.

A copy of the receipt has been sent. Efforts of trying to contact the person handling the matter have been futile at best. The reference number is XLI-288945-M1D8 and the amount in question is R3760.00

Please step in and assist as I have exhausted all possible means within my disposal.

Thank you in advance.