Worst nightmare as I cancel lease b4 the end date

I have had to cancel my lease due to the office being closed due to the rise of Covid cases and I informed them in writing that I can pay for the January lease as I cannot pay the rent and the storage. They informed me that they have a person moving in on the 1st January.

B4 the viewing of the new tenant, I had specifically mentioned that I will be moving back to Durban and I will leave the key. I also mentioned that the person I am leaving the key with will be leaving soon for December holidays but they told me all is great as they have the spare key. Shortly after the person I left the key with left for their holiday, I was told that I need to get the key otherwise I will be charged with 700. I had to post the key from EC to get to CT in time as I didn’t have the 700 to give away.

I then informed the agent that I have booked and paid people to move for me the 31, I was informed that will not work with them again I had to make other arrangements and I had produced the proof that I have made the changes of the truck to suit them and move on the 29nth. On the 31st after I had done all that they are now telling me I’m at fault for canceling and my deposit is being discussed even after I had already paid for the cancellation fees.

Please help me as I am unaware of how to resolve this issue