Application denied

I have a contract with vodacom for about 8 years and im in credit meaning i pay upfront instead of every month so there is in your accout R1000 of my money. now the sales staff are telling me that somewhere i did not pay my account wel i have statements to prove that i am good paying client never missed one payment my contract now is R119.50 and there is more that R1000 in vodacoms account so that is for the next 9 months so how did i miss a payment or how dont i meet the minimum requirements is R5500 not enough and in a months time it will go up To R7000. so i am very confused now. Please get back to me on how to solve the problem, because i asked the people how are we going to solve no they can only help me on monday or so?????