Using sfr 3G connections with an n900 require that you change some parameters if you have only a ‘Pass Surf’ option in your contract.

First in the connection manager you need to select your mobile connection and change the AP. Instead of websfr use wapsfr.

As wapsfr is restricted to http,https, and dns you can t use all features available on n900 like instant messaging or email.

There is also another restriction using wapsfr means that you also use the wapsfr proxy which doesn’t answer to request from unknow mobile user agent or desktop user agent. For example the proxy deny any request if the user agent contain the word ‘firefox’. So you need to change the user agent for something else by using about:config. For example i use : ‘Nokian95′, but you can also use the iphone user agent.