Refusing to payback deposit

We stayed 20 years at the Fire Department housing in Erasmuskloof Pretoria. We gave 1 month notice and requested our deposit to be paid back to us together with the interest of the deposit. City of Tshwane refused to pay back any amount that is due to us. The just say that there is NO refund to be paid back to you. We went in to see them and they are full of stories to refund us what is due to us. I also understand that you first stay and then you pay, but according to the city council, it does not work like that - for them is you first stay and then you pay - how ridiculous!! All the other places is that you have to pay a full month rent and deposit before you can start renting. We are now struggling 6 months to get our deposit back as well as the interest on the deposit of 20years. According to them we are also behind with the payments but we have all the proof per month on the salary slips that we have paid as given through by housing to the payslip division. They even took on the last day of the notice month again another instalment and does not want to pay it back. Mails sent forward and backwards without any correspondence from their side - don't care.