Rental deposit

I've got a problem with this Institute my rental agreement has expired and now I an renting through the owner but the rental agency that I used to rent from just told me that they will not pay me dack my deposit, I've never got an invoice form them and I used to pay every month, never skipping I've send emails to them asking them to repair things they never come back I've got the proof of the emails, he never came back to me like the previous years and asked me if I wanted to extend my rent but the owner came to me and asked me to rent from her directly and I'm doing this but only when my rental agreement ended but still the rental agent says my contract is not finished I've got the agreement with his signature on it I don't no what's his problem, can enyone help me or what can I do