Mtn is A Disastrous Network Provider

I am very disappointed with Mtn. Since 2009 I had account with them, only now they are costing me not to apply for a mortgage loan. Since March I had contacted Mtn call centre numerous times. There is a write off default of R342,400 and lenders are asking for proof of payment for this. All I am told that I am not the only one, but that doesn't help as i want to apply homeloan now. Account is paid up to date.