• Rule 2. If you are wanting a new phone or other free gift, shop around for the lowest priced monthly deal and toss the sim card in the bin.

The networks offer such aggressive retail deals, and rely on the user to pay the substantial premiums on usage of peak and per minute billed airtime to recoup the profits. They lose out to those astute users who throw away the sim card but use the new phone and free gift.
Look for the best valued airtime deal - lowest per second rates and peak rates to all networks.