Connect with Powershell to your Exchange Online.
Run this command to list all users and mobile phones:
Get-mobiledevice | select devicetype, deviceos, identity
Add | out-grudview if you want the ability to group the list after for example mobile phone type.
Get-mobiledevice | select devicetype, deviceos, identity | out-gridview
You can also list users with a specific mobile phone. For example Samsung:
Get-mobiledevice | where {$_.devicetype -match “Samsung*”} | select devicetype, deviceos, identity
If you for example wants to delete all Samsung and HTC partnerships you can run this command:
Get-mobiledevice | where {$_.devicetype -match “Samsung*” -OR $_.devicetype -match “HTC*”} | select identity | remove-mobiledevice