Investcon Rips you off and does a half job

I hired Investcon to repair some roof leaks in an emergency. The work was valued at +-R45000 later however they charged me R137 000. They then repaired the roof but it kept leaking after several revisits to the site to fix the problem. When i asked for my money back or I would take it further, they said I can see them in court, even though they provided a written guarantee which I had requested. The workmanship was very shoddy. They even sent me an invoice in the end which dudnt specify the work in detail and it wasnt even adressed to me, but to some ither client. I had requested this so he could justify the cost which seemed extreme for the scope of work done and for tax. I never received it to this day.