Billing Department - ***********!!

My Landline number has 2 accounts. The reason for 2 accounts is that the account ownership was transferred from my mum to me. The active account which is in my name, is in good standing and settled monthly bia debit order. The cancelled account (previously in my mum,s name) is in a credit balance. This is due to EFTs being processed monthly for more than 6 months in error. The billing department keep rejecting the refund citing that the current account is settled. They simply cannot understand that the refund relates to the cancelled account. How *********** can one be ?