Stuck in Loop for Psychiatric Treatments

I have been facing mental health issues and recently visited the Psychiatry Department at a Government Hospital. The doctor prescribed some medicines, but these are not available in the government hospital, so I have to buy them from outside. I approached a charitable trust for help, and they agreed but asked for an expenditure letter from the treating Psychiatric doctor. When I went back to the doctor for the letter, he said that expenditure letters are only given to admitted patients and refused to provide one. Now, the charitable trust says they can’t help without the expenditure letter, and I’m stuck in between. What should I do now? Is there any way to get help from the charitable trust for my medicines? Or Doctor lying ?any advice is appreciated