Outbound call default call display number

[Tim_question]

Hi

I am using Fongo Works on iOS and I have ported my phone number to Fongo Works.
When I make outgoing calls using Fongo Works app it asks me: Make Call As: and lists 2 numbers (the originally assigned Fongo Works number and my ported number) and the Hidden option.
How can I make a default option selected automatically so that I do not get promoted every time I need to make a call from the app?

Thanks