poor reception and download speeds

I've never come across a service provider with such poor service, for over a year now I have been facing problems with cell c's network and internet speeds, I have 3 contracts and been loyal to cell c and yet they never seem to have a solution to my problem, my download speeds on all three contracts are ridiculously slow and been having network issues with my main sim ( poor call quality and dropping calls ) when I go into the branch they keep telling me to sim swap, which I have already done! It definitely doesn't help, really wish Vodacom had an option to buy me out of these contracts. This is extremely frustrating