For clarification, are you using AF to update information in AD, or are you updating AF to specify the account to use for querying AD?
Our system is configured as 'Use the account the PI AF Server runs as' and I've been able to search for accounts and fine them, both accounts that have phone numbers and accounts that don't.
I tried to update my profile data (adding a phone number) and saved the changes; the system didn't indicate the changes were NOT saved, but when checking again, the changes are not there.
Can you confirm the AD changes did take effect?
I had the AD Administrator update several personnel records in the AD (GAL) with cell phone numbers.
I can see those changes in Outlook, but when I try to access the data in Pi Explorer, I see no changes/updates.
What version of PI AF are you running? I just tried in the 2018 version and this works fine in my system. Did you refresh the client or tried to search for the contact again? Also, are you certain you are referring to an AD contact (grey icon) and not an AF contact (green icon).