Home-Connect ISP

We have been with Home-Connect for less than a year. We signed up on a special offer on a home Fibre connection that they advertised. 30mbs download and 3mbs download. Short while ago they sent us a notice that our monthly rental will increase by 80% in price per month. I sent multiple emails with the contract attached that I signed and the agreements stipulated in it. Since then our line has been very slow. Sometimes at 1Mbs download. I have sent emails, logged calls, but no replies are received. Nothing. Worst service.