Turn off mobile phone notifications
If your users have mobile phones and tablets with Skype for Business installed, they can receive alerts about incoming and missed instant messages.
On Android and Windows Phones, Skype for Business notifications pop up in real time. For Windows Phone, iPhone, and iPad devices, however, push notification is used to show the alerts whenever you’re not actively using Skype for Business on your phone or tablet.
Turn push notifications off for all the Windows Phone or Apple devices in your organization
Go to Organization > General.
Under Mobile phone notifications, clear the box next to the notification service you want to disable, and then click Save.
Keep in mind:
If you turn off push notifications, users still receive all alerts when they start up Skype for Business again on their mobile device.
Push notifications are turned on by default. Individual users can turn them off by choosing the appropriate Skype for Business option on their mobile device.
When you turn off push notifications, users can’t turn them back on.