No gas certificate authority

Mike contacted me after I looked for a gas installer on a website. He gave me a good price to install and certify my gas hob installation. After messing me around for weeks with no shows he eventually sent two guys to connect the hob to an isolater and gas tank. These guys had no idea of what they were doing. Did not have all the tools and we're ***********. They promised to send me certificate by email. Mike kept telling me he sent to my 2 different emails but to date I am still waiting. I don't think they are even authorised to issue certificates. The guy checking for compliance only checked if the gas plates came on. No other checking. Stay away from this company