"MRI scan referral declined"

I have now had a extremely bad shoulder injury since 2011, I have been to the doctors a couple of times about this.my private physiotherapist wrote a letter saying it needed more investigation into it. I am a professional swimmer and hoping to get to Olympic trails this year but I can't with a bad injury. Although my sports coach and physiotherapist have asked my doctor for a MRI or some sort of scan, they have declined which is now going to impact yet another year of my training and racing which I can't afford to have. (Not sure on accurate dates but the latest was phone consolation as a appointment was going to be at least 3 weeks time which is not good enough)