I want to extend my Chinese visa.

In the Netherlands I got a L (study) type because I study here (Beijing) for two months. In Holland they said if I wanted to travel, I could extend it here in China. However, when I went to the Visa application centre today, they said it impossible to get a new F one; my school also doesn't want to sign for an extended stay so that I can get an extension on my L type. Is it really impossible to get a new travel F one? Or should I try again?