This is normal. Because Celcom is not official in iPhone model.

It can be fixed if u jailbroken the devices. Change some settings.

Else, u have to wait for celcom to join Official iPhone supplier and the new network settings updated from itunes sync.

Btw, i think the setting is evil.

When i was using my digi before digi official iphone supplier, i can disable the gprs charges using fake apn/username/password.

but once digi in official iphone 4 network, whatever i set wrongly, it will just go thru and keep charging me my gprs charges.

And no refund from digi as they say it is not there problem. but it is their problem as ios ver3 does not have option to switch off the gprs/3g setting.

Regards,
koonming