Question for Virgin Mobile iPhone users (USA)

Hi,

I just activated my Virgin Mobile iPhone 4S tonight and I had a quick question. On previous iPhones that I've had with like AT&T or Sprint, I could have sworn that my phone number was always shown in the phone/kepad app above the keypad (but I could be wrong.) On my Virgin Mobile iPhone, there is just a blank space above the keypad.

I wanted to ask and find out if I was mistaken about the previous phones I've had or is it a feature that was removed with iOS 6 or is it a Virgin Mobile thing?

Thanks!