How can I show the contact number of the Dialed contact
Unfortunately, you cannot display the number of a contact while calling him. However, there's a way of identifying the number you are calling by adding a custom Contact Label.

To do so:


Open Contacts app
Search for you desired contact
Tap Edit in the top right corner to edit your contact
Tap the label next to the number on the left. (see image below)
Choose a label for that number (see image below)
Do the same for the other numbers


Then, when you call that contact, the label will appear directly below the contact's name.