Hi Will,
Seems address book of phone cannot capture the phone numbers from Delve and SharePoint App correctly. Per my test, my Apps works fine. You could try clearing cache of phone and reboot to re-sign in your account to ensure this issue is not caused by 3rd party Apps.
If the issue remains, I would like to confirm following information to narrow down this issue:
1.Does the issue occur in all contacts in Delve and SharePoint App?
2.When did the issue start to happen? What changes did you make before? For example, Office Apps update, etc.
3.Does the issue occur in other Apps when you attempt to dial from the device?
4.If you use another phone with the same account, does the issue persist? Do your colleagues in the same tenant encounter this issue? If your colleagues sign in their accounts in your phone, does the issue occur again? This is due to confirm if the issue is related to phone or account.
5.Please share your current SharePoint and Delve version with us.
Regards,
Eli