Getting help

For a long time I’ve known I’m depressed but my mom told me I had nothing to be depressed about. That was when I was 12, I’m 18 now. She wouldn’t let me get help but now that I’m 18 I can. My boyfriend and my grandparents (who I live with) agree that I should get help and get diagnosed with something and get help for it. I have the number for the place in my town but I don’t know what to tell them or ask for for that. Can anyone help? I have bad anxiety and hate talking on the phone and I don’t know what to ask for to have that done