Extract users cellualar/mobile numbers from Exchange 2013

Hi, we are running Exchange 2013 CU7 and I have been requested to extract data for all the users that are using ActiveSync to their mobile devices for email. Part of this is to populate their AD account with the Mobile number they are using.

I have all the powershell scripts to do this apart from one, tiny component..getting the mobile number. Using Get-MobileDevice or Get-mobilDeviceStatistics only provides me with the final 4 digits. Does Exchange 2013 hold the full number somewhere? Can I access this somehow?

I am using PS version 4.

Any advice appreciated.