Fidelity ADT refusing to cancel my contract with them

My name is Maropeng Mphelo residing at 80 leadwood street in Johannesburg. around the 25th of January 2023 i sent several emails to Fidelity ADT to cancel my alarm contract with them. Every month i was left frustrated with this company for charging me the contract amount, e.g., i used to pay between R700 and R800, but on top of this they will bill extra R376 every month. when i asked for refund, it will take them around three months before they can pay it back. they keep sending their guards to my house even if i didn't press a panic burton. Can you please assist me to cancel this contract.