Cell C ripped me off, promising to upgrade but they downgraded me instead.

I have been ********** by Cell C. I asked to be upgraded to 50Mbps but I am receiving was lesser than even 25Mbps. I tried several times to get them to sort out the slow speed issue but no one is willing to help. they keep sending emails saying they tried calling me and I know they are lying. No one can help me they tell me one thing after the other and if I dont receiving proper upgrade of 50Mbps with speed that can accommodate 4k as I asked for I will terminate my contract. Sort this issue now cause I know you are lying to me. 50Mpbs is clearly a lie.