Have you installed the drivers for the Wifi Card?
Does the Axim recognise the card?
Does the card appear to activate? Do you get a flashing light?
If it asking for a phone number it is trying to use the wrong settings.
What type of card is it?
You need to install the correct drivers for the card and then you should be able to turn the Wifi on and connect.
Look on the manufacturers website for drivers.
You may find the answer to you question in the Wifi Forum
Or more likely in Ikehikers excellent Wifi guide