Poor service.

I have been with MTN for the past 10years and they always had been my choice but here I am finding myself have to complain about their bad service. I took a month to month contract of which I paid an upfront payment of R473,90 .on that amount I was told it's a pro rata for May and June fee. On the 4th June they tried to debit R693 .call them to find out why so much I was told the R473 90 was not appearing on the invoice and I sent through the email that confirms I paid . I have been calling with no luck or help .this is frustrating as the finance wants the proof of Payment in PDF . Just want to thank the last person Sisipho Makamba who tried to assist even though she's not in finance where everything gets stuck.