Has anyone ever used an O2 mobile to connect a PDA to the internet?

Although I've got a number to dial into, which I knows works, I am unable to make a connection.

I've tried contacting O2 techincal help, but any assistance they have provided has failed to resolve the problem.

I have proved connectivty in theory using a different SIM, but still struggling with O2.

Any advice is appreciated.

TIA