Which App? Blackberry Work, Blackberry Access?
What Platform? Good Control? UEM?
What device platform? iOS? Android?
Not nearly enough information to give an accurate answer. I will attempt to answer. My answers will focus around Good Control.
For Good control look in the application policy.
Good Access has a check Box allow Telephony:
Blackberry Work under the interoperability tab, make sure Voice and SMS check boxes are checked.