About Certification from Abroad

Dear Sir,

I got my PhD from Japan on 2011. Now I am in Bangladesh and trying to apply for a Postdoc position in China. The China University asked me to verify/certify my PhD certificate from Chinese Embassy. I went to the Chinese Embassy located in Bangladesh. But they said, they cant verify my PhD certificate because it was issued from Japanese University and only Chinese Embassy in Japan can verify that certificate.

In that case, how to do it? I found Chinese embassy website not in English and the telephone receptionist dont understand what I want to say. Please help me. I cant go there right? I can only send the original certificate by post if they want.

Waiting for a help please.