Telkom refusing to give me my money back even though i have cancelled the contract

When I opened an account with Telkom they took a deposit of 3000 Rands as i m not a RSA citizen and it appears on my statement every month. I cancelled my contract and now call centre agents say they don’t see it on the system and they can’t help me in this regard whatsoever. I'm being told i need to provide them with a bank statement that proofs that i paid the money.... this money was paid 2 years ago, do they know that banks charges for bank statement why do they want a bank statement if their monthly statement states that i paid it.

I cancelled their contract now I want my money. Please help.