Problems with 3.1.3

[Dphone]

I've had my Iphone since January and never had any problems. I recently downloaded the new OS and now I noticed little problems here and there. For one my phones seems to be running a little slower, both on Safari and apps loading slowly. I have some issues with Facebook that i never had before.

Is there any way to go back to the old OS i had before ? I think it was 3.1.2.

I'm not jailbroken.

 

[en0c]

No. You can't downgrade your iPhone if it's 3GS.
Restore the iPhone and set it up as new.