Cell C customer service and accounts department

Its been 4 days going up and down with cell c about a payment i made on may from their cell c app. They telling me it does reflect on their side but it shows clearly on my statement that the payment is been made but they say don't accept the statement as a proof of payment. They making me go up and down for their own app fault. I can't find the proof of payment they are looking for. Now their app lockwd me out. They telling me the money is there but they can't allocate it. If they can't what am I supposed to do because its their own app. I have done my part by paying. I paid using the same app for June. It reflects then now whose problem is this. I have sent them emails attached with my statement that shows the payment was made and to the brunch and spent more hour without any solution but still they are failing even though I showed them the bank statement