Cloud Connect overcharging?

I have been a client of their's for almost two years. In that time I have never received the download speeds that I pay for. I had a 6mps line and this sometimes only gave me 1mps. When I called in they would make adjustments and the speed would be better. I have complained several times over the period but just falls on deaf ears. They changed an installation point and even this I was way overcharged and after a lot of fighting and argueing they eventually refunded a small portion. The work itself was very badly carried out. I am still waiting for an answer to what appears to be overcharging for a very slow data line.