UC, Lync 2013, Call a Lync Contact in Lync 2013 for iPhone
On this page, you can learn how to call a contact in Lync 2013 for iPhone.
To call a contact who is on Lync, tap Contacts, find the person in your Contacts list, or type their name in the search box. When you find the contact, tap their name, and then tap Lync Call or tap the Phone icon. This will call the person on Lync.
Depending on how you set your VoIP call options, when you make a call
it could use Wi-Fi or your cellular data plan.
For more information, go to Manage Wi-Fi for VoIP options.