You are the Office 365 administrator for your company.
You need to configure Microsoft Lync Online to disable alerts for voicemail and instant messages to Windows
Phones.
What should you do? mobile application is inactive. Push notifications notify a user of events such as a new or missed IM invitation and voice mail. You can enable or disable push notifications for Windows Phone devices by using either Lync https://technet.microsoft.com/en-us/library/jj688162(v=ocs.15).aspx

A.
In the Lync admin center, disable the Microsoft Push Notification Service.

B.
Use the Set-CsPrivacyConfiguration Windows PowerShell cmdlet.

C.
Use the Set-CsUser Windows PowerShell cmdlet.

D.
Use the Set-CsHostedVoiceMailPolicy Windows PowerShell cmdlet.

Explanation:

Push notifications, in the form of badges, icons, or alerts, can be sent to a Windows Phone even when the
Server 2013 Control Panel or Lync Server 2013 Management Shell.
References: