Someone’s not doing their job

I am having a huge problem with cartrack upon singing a contract with them for my car. I was told to make a pro rata payment which I made and sent emails to various people (3 email addresses to be exact)working there providing them with the proof of payment. The payment was made on 27th of May 2021 already but I am still being harassed about it even today. I find myself explaining myself over and over again they called me Saturday and said they have received it and will sort it out but just now i got a call regarding payment. Please assist me as I fear should I encounter issues or problems with my car they might say they can’t assist me because I did not pay when I actual fact I paid.