Telkom

I bought a Samsung A51 dual sim on contract with telkom on the 31st of January 2020. The phone started to randomly freeze and restart when I tried to make phone calls. I took it to the store on the 29th of February 2020 and it was booked for repairs. On the 11th of March it came back but now it has a new problem. It no longer works as a dual sim. I asked them what I should do and they are telling me to book it again for repairs. I asked about exchange procedures or how to cancel but apparently those options are not available to me. How do I deal with this? I mean I feel like I am paying for a phone that I am not using.