where do you live? generally i mean... if you are in canada then look for your local branch of the CMHA, they can help you as well. They are well versed in dealing with the local clinics. You could go to one of their branches and explain to a worker there, ask for help.

If you live elsewhere... first suggestion is like the others, go there in person. Perna's idea is a wonderful one too.

If all else fails? Go to outpatients or the ER and tell them you have been trying to get seen but no one wil talk to you or return your calls. That is what a friend of mine did. The outpatient staff were not happy with the clinic intake people and he had a pdoc on call come and talk to him and they made an appt right there.