Unable to locate my payment

I have had 3 cell contract with Cell C Service provider. I called in to get settlement amounts for all 3 contracts. Once I had these amounts I then decided to settle all contracts once off and made 3 different payments on the 23rd May 2019, paying up all my contracts. When I called in to cancel the now paid off contracts I was advised that only 2 payments are reflecting. I then enquired about the 3rd payment and it turned out that there had been a mistake on the reference number therefore the payment was not reflecting. I sent through my proof of payment in order for them to locate the payment for me....I've contacted Cell C since the 24th May 2019 and everyday when calling to follow up on the matter I am being asked to send through proof of payment to different consultants. I am fed up of contacting Cellc and sending proof of payment everyday....I just need for them to locate the payment made and close of my last remaining contract....this is by far the worst experience I have had with cellc in the past 7 years of being their client.