To check whether the intellectual property agency has qualified agents, you need to go to official website of the State Trademark Office. As far as this issue is concerned, if you want to inquire about the agencies in Hangzhou, you can enter "Hangzhou" in the address bar to inquire about the 292 agencies registered in Hangzhou.
There are detailed information of these enterprises at the bottom of the actual query page. Name, address, telephone number, etc.