"Not being given an appointment with a specialist"

I am absolutely frustrated trying to get help for my painful knee. I initially visited my GP who was very good, but unfortunately the pain did not improve. He suggested I went to physiotherapy - this is where the problems started. I was told I had to self-refer, but found it difficult get information about the process. When I hadn't heard anything for 3 months, I finally got in touch with someone who told me that the waiting list was 18 weeks long. I went back to see my GP as I am not sleeping and needed painkillers most days. He said he would refer to me to the orthopaedic department at Glasgow Royal Infirmary. 

The next thing that happened was that I got a letter from the orthopaedic department saying that they don't see these conditions anymore as they are considered minor. I was told that if I wanted to speak to someone I had to phone a telephone number of a certain day within a 90 minute window. This is just not possible with work commitments. I have never come across something like this in all my previous hospital appointments. When I did try, the phone was engaged. I spoke to my GP who said that this is happening more and more. 

I am considering using my savings to see a consultant privately as I don't trust the NHS anymore!