When a Skype for Business user receives an on-screen call notification, an email about a missed call, or other notification from Skype for Business, the notification may contain phone numbers or other data that are personal/private and not published in the TTU Active Directory.
The information is coming from the Outlook Contacts of the person who received the notification, not from Active Directory, Banner, or some other source.
When you receive a call from someone whose number is stored in your Contacts, Skype for Business will take the info in your personal Contacts combined with the information in the ttu.edu Active Directory and use all of that data in on-screen pop-ups, emails, or other notifications you receive from Skype for Business.
No solution is necessary. The system is working as intended.