Hello, 

I am working for a company that requires to hide the information of the users addresses and phone numbers from users. 
Basically we need to make sure that end users can not see contact information such as Address and Phone number of other users. 

This information could be hidden by an administrator in previous environment / versions of Exchange by modification of the Default Template details. 

But I have been unable to find how to do this through the office 365 cloud solution. Can I please have some assistance on this, I am sure others may have come across this.

(to clarify, I am not wanting to hide users all together, simply edit the visible attributes that people can see in the GAL)

Hi,

In On-premises Exchange server, we can use the Details Templates Editor to customize the client-side graphical user interface (GUI) presentation of object properties that are accessed by using address lists in Microsoft Outlook. However, this tool isn't visible in Exchange Online.

I suggest we can ask a question in Exchange Online forum to confirm whether there is any workaround for your requirement:

https://social.technet.microsoft.com/Forums/msonline/en-us/home?forum=onlineservicesexchange

Regards,