Billing Query

my father had contract with Nashua , it was moved to MTN when Nashua closed down. he has had massive issues with MTN saying the is an amount due and he has never missed a payment, instead MTN increased his payment with R100 when he queried they fixed it only for 1 month and it continued , instead of him complaining he decided to pay with the new amount. we spoke to a Tshepo at Maponya and he said the credit was done and the account up to date he's waiting for headoffice to approve the amount and he will come back to us , he never come back & us we always have to call him to follow up, telephone bills , petrol driving from Lawley to Soweto to sort out the matter. right now the account is owing over R400 again but no one can explain where this amount is coming from and they keep blaming the system. Right now the account is suspended after he did an upgrade due to this account, he has never skipped a payment but always an amount outstanding