*sigh* freakin gate keepers.
I went through this trying to get my hormone letter. The therapist was a post op TS, which I thought would be a good thing. I had already been living full time for about 3 years, was perfectly comfortable with my being trans and after 3 months of visiting her, she still didn't want to write a letter. I simplly wanted to start HRT. I then told her "This feels like you are just milking money out of me for as long as you can drag this out, are you EVER going to write a letter? Or is this just an income stream for you, screwing over TGs..." Her reply was "I feel this hostility is coming from your mother still trying to control your life", to which I said, "Wow, that would be a neat trick given she has been dead for over 5 years." We ended the session and she wrote the letter the next day.
As far as your problem, go there in person. If they are busy just say "fine, I'll just wait out here until they are unbusy". Do NOT let the receptionist offer to "give then a message". I've had to deal with so many doctors about trans stuff getting meds etc that put me on ignore, I've had to do this myself several times. Them not refilling meds when they said they would and then not returning calls etc etc. Going there in person and just camping out has worked for me.