Deposit never given back by Telkom

I have cancelled my landline due to continueous cable theft. Telkom has promised me that they would give me back my deposit of R700 until my final account ( as it is stated On every statement i have received). Im no longer with Telkom and i've paid every amount which was owed. Its now been months and months and i've never ever received my deposit! I've even phoned in twice and they keep on giving me excuses. If ever Telkom wanted money, they deduct from my bank account, but now that they owe me, they dont want to give me my money.. i dont know what to do anymore...please help!