We sometimes see that numbers are not properly stored on the SIM card and thus don't show on BES. To check this, do the following:

On you Blackberry, go to Options > Device > Advanced System Settings > SIM card

Under "Phones numbers" check what is there. If no number is there or if it is wrong, high light it and press the Menu button, then choose

Edit SIM Phone Number

If you wait a day or so, it should come down to the BES. Or you just do a re-activation to get it quicker.