When you book a flight through your account on your own, it uses your number from your profile and populates this automatically so no issues there.

I've also found with corporate bookings, even though my company system has my phone number, it never actually puts it into my reservation... so after corporate books my ticket I go in to the itinerary and add my phone number to the contact info. Annoying since I have to remember to do this every time as they could never figure out why their Concur system doesn't fill in my phone number.