Lack of Forthcoming with credible information

I logged a warranty claim through the Discovery Insure Warranty Policy I have taken out on my vehicle. I dropped my vehicle off with the same provider I always use, and also services my vehicles. Now Discovery comes and says that the provider is no longer on M-Sure's approved list. Both me and the provider directly contacted M-Sure and they confirmed to us both that that is not the case, there is no complaints or actions against the specific provider. But Discovery still insists there is and wants me to sign a disclaimer that I need to pay the additional costs, even though my profile states that they cover the full amount up to the value of the vehicle and R0 excess when using an approved provider, which M-Sure confirmed they are, but Discovery Insure says no. We have asked multiple times for proof from Discovery on this and to disclose the source where they get this "information" but we get ignored on those requests. Discovery service has been declining more and more.