I have not found an answer to my problem that worked on the forum yet. After updating the fairphone to Kola 1.8 the internet connection got very (!) slow. Wifi connection works. I have tried to reset the phone but that didn’t sovle the problem.
It could be that the update has affected your settings (even if it shouldn’t). Go to
System settings > Wireless & Networks - More > Mobile Networks.
Check that 3G Service is enabled. Also check that your APN (Access Point Names) settings are as recommended by your network provider.