Sky Build

We had a hip to gable and dormer loft extension shell done with a complete new roof by sky build and now after 7 years we have a leak from the roof where the dormer joins the main roof and water is running down the internal wall. I contacted Mark and the roofer who came to look at where the leak was coming from and after a month they are now telling me that only the flat roof is covered by warranty and not the rest of the roof even when it was completely replaced as they say things can move ; “ie strong winds and adverse weather conditions,” even though there web site says “fully insured and covered by a no-fuss guarantee.”
Mark also messaged me saying “You do not get a life time warranty unless agreed in writing.”
This is very disappointing that they won’t fix a leak and rectify their work when asked to even after I’ve shown them my receipt which Mark asked to see as proof.