T-Mobile chose to "break the mold" when they moved into their flat-rate plan with embedded taxes and fees, and it was so successful it seems to have ultimately forced the hand of other providers to follow suit.

Is there any information about the steps T-Mobile took before they went in that direction initially? Did they do intensive research to gather feedback on variable bills, complex bills, or other existing norms of cell phone plan billing practices of the day before they revolutionized their pricing model?

How long did they work to evaluate that new paradigm before they dove in?