Telkom refuses to give back deposit owed.

Due to cable theft, i have been told that the cables wont be replaced and that i have to cancel my landine with Telkom -I've done so. I've paid all outstanding amounts so i don't owe Telkom anything anymore. But now i have a huge problem : Telkom refuses to give me back my R700 deposit which they owe me. It says the following, on every statement i have, "Deposit retained until final ***". Its now been months and months that im finished with Telkom, but never received my deposit back! I've even called Telkom twice and they keep on giving me excuses! I dont know what to do anymore...please help.