Just Property Kroonstad chance my rental expiry date, to keep my deposit

After my rental contract expiry date was on the 2017/11/30 to 2018/11/30 after I in form them i will rent from them but diretly from the owner, after complition of my contract them that exrired 2017/11/30, on an statement sent to on the 12 December 2017 it shows my expiry changed to 2018/11/30 and they deducted R 2 505.00 from my diposit. I'm still waiting for an respons for an e-mail I sent them, asking how they come up with this amount. I didn't open my e-mail before the 23 December 2017 and thats wen i saw the mail from them. I treid calling them on Monday the 25 December 2017, office was closed, Eventually I got hold of the agent how rented the apartment to me and ask her how they came up with the dedution sence there was no brige of contact and no damage to the apartment, she laughed and said she does not work with billing, I must phone the office 4 Jan 2018 wen they open. On the 4 jan 2018 I phoned the office to enquire, the phone was droped 3 times. the forth time i to say i will get legal assists. After 1 minute Braam phoned me, I asked him why the amount of R 2 505.00 was deducted from my diposit of R3 350.00 he said it was penalty for that I'm going to rent straight from the owner. I ask him was i in brige of contract was there damage to the aprtment, he only said penalty and i must not threaten his staff with legal action and he has more than 300 customers. I reqeusted he put the resons in writting and mail it to me because i'm not happy of what they did does not make sence, My contract with them was from 01/12/2016 till 30/11/2017 not 2018. Was later informed that I'm not the only person the are lot of peaple in Kroonstad that was done in by Just Property in Kroonstad in the same way. I will take this furthernot gonig to let this slide.