US citizen born in Iran- visa application

I was told by a visa agency that because I was born in Iran I have to apply in person for a china tourist visa, even though I am a US citizen. To verify this, I have tried to contact the China Embassy and Consular offices in DC, NY and Houston but there is no answer or busy signal at the telephone numbers listed. I sent emails and so far received an automatic reply in Chinese. Any information on this would be greatly appreciated. Thank you !!!