Owner of house I bought refusing to pay back rental

In January 2021, I made an offer to purchase an apartment. The process was long and frustrating with lack of communication from the transferring attorneys as a result they only lodged in November 2021. The place was empty so in April 2021 I took early occupation and signed a contract. The contract stipulated how much I had to pay in rent and because water in included in the levies, I did not pay for water. Electricity was prepaid. On the 30th November 2021,I paid rent for December in the morning and later that day, the property got registered. The owner is now refusing to pay back the rent I paid for December. The owner claims that I had to pay for rates at the City of Johannesburg. That's was not part of the contract and to the best of my knowledge I did not have an account with the City of Johannesburg but the owner used the fact that the money was in her account as a way to act in bad faith and manipulate the whole situation. She has since blocked my number and the estate agent, transferring attorneys have not been able to assist. I am frustrated and want my money back. I don't k ow what to do.