RE: Visas in general

Check with the PSB Visa office for the official line first and call back later while noting the name of the person on the other end of the phone.

Then if you do get an "agent" to extend your visa in China, make sure that they have a good record by asking a few friends how they got theirs.

Some of the cutie pie avatars paired with tags like "Lilly" "Chi Chi" and "Amy" look dodgy. If they really had such good connections they'd be too busy dealing with companies, not answering threads on forums.

Recently, there's been a spate of passport thefts by people that trick people into handing over their documents, its your passport.... be careful!

The situation during Shanghai expo will be the same as during the Beijing Olympics 2008.

You are still able to extend your visa.
The limitations are related to some types of conversion such as the L to F conversion. But it doesn't mean to forbiden all of the visitors.

Extend your L to 3 months or 30 days~ as what you like.

the PSB is located at Yonghegong Lama-Temple Station. You can take subway line 2, get off at Yonghegong station.

Kind Regards
Grace