Telkom owes me money.

I had a mobile contract with Telkom for 24 months after which i changed to prepaid service last year November 2017. Telkom still deducted the debit order from my account after admitting on a recorded line that THEY made a mistake. They owe my over R 1500 till now and every time a call them their system is either being updated OR does not respond. Give my my damn money.