What my requirement is "I need to wake up my application from the background when a call comes in my iPhone".Is Any way to do so? Shall we get a unique number for the each user in
You'll need to use PushKit notifications and CallKit that can start the app even when the app is killed.
The CallKit is not really absolutely necessary, since it "just" allows you to provide standard calling interface. But it is a very nice feature to have - user is used to standard iOS interface for answering/declining calls, so I would definitely recommend to go with CallKit, instead of just standard notifications.
You can take a look at this tutorial, or just google together the PushKit, CallKit and Voip to get other relevant tutorials.