Unrefundable deposit

We were renting at one of afcho property at peacehaven Andrea closed vereeniging, we signed 12 months contract but we moved out out before contract end. When we moved in we paid 6300 deposit but rent free according to our credit score, we gave 1 month notice as they require, they refuse to give us deposit and now they are saying we owe them 2100 we don't understand how bcs the we signed the contract they said as long as we gave notice we will get our deposit back

Can you please intervine