Won't reply mails due to owing me my Deposit

I've ended my contract with the agency, (12 month period) within 6 months and moved to KZN due to circumstances and new lodgers moved in. I've requested my deposit refund but they're now completely ignoring my mails, last mail was telling me that I owe them a payment, I did liaise with them but they're now completely ignoring me, this is now settling as bad dept at the bureau and I'm unable to get my deposit back. I won't recommend this agency to anyone.