No follow-up for 10 months, no correspondence and now harassing me every day

In April 2023, Discovery medical handed me over for an account. I already had arrangements with them and was paying the last R1000 off over 4 months. An agent from SSDA phoned me in April 2023 and I explained to her that Discovery shouldn't have handed me over and that she needed to follow-up with Discovery. I never again heard from them again as I paid up my account with Discovery. Then after 10 months since that conversation, on Friday the 02/02/2024 I got my first call. I told the lady I never heard from them and also never received any written notice from them, I didn't even remember or could recall knowing the name of their company. I never changed my phone number in that time, I have the same email address for the past 16 years and the same phone number for the past almost 24 years. I explained that I will not pay this account, which obviously has now collected interest as I wasn't notified that Discovery didn't withdraw this account. Now since Friday the 02/02/2024, I also received a call on Saturday 03/02/2024 and today 05/02/2024. I would like to have a call from one of the lawyers please as their seems to be a huge problem in their company with staff not doing their job and then suddenly start to harass people. I also I'm aware that they charge for every phone call made to me adding it to my supposed bill!