[inquisitor]

What is their customer care actually good for, if they can't even manage tariff options?

O2 (the network Fonic use) have a way better network with decent data rates. However with your LG Cookie you will never experience really fast connections, as it supports only GSM/EDGE, which means the fastest possible data rates are ~200 KBit/s. However all GSM/EDGE-networks in the Western world suffer from high loads due to the increasing number of smartphones and GSM-networks are quite prone to congestions. So those 200 KBit/s are just theory and even the better networks won't deliver significantly more than 100 KBit/s.
If you really want fast and reliable data, go for a Fonic SIM and a HSDPA-capable 3G-handset (supporting the European 3G frequency at 2100MHz!), which enables you of using 3G networks, which in practice will reach download rates of 2000-3000 KBit/s, sometimes even more.