3G 2.0.2. GPRS on PAYG iPhone

I am one of those who purchased an iPhone and used a PAYG sim including the unlimited web and wifi bolt-on. Everything worked well till the upgrade from 2.0.1 to 2.0.2. Now I have no GPRS connection to the web any longer. Everything else works fine but no Web access. It is almost impossible to down-grade to 2.0.1 without jail-breaking which I do not want to do.
Apple should include a software down-grade feature for those whom might have developed a problem as a result of upgrades. But that would be too logical I guess, even for Apple. Think Different ?
Powerbook G4