[jbearamus]

they strike a balance in price between the two plans so you get charged fairly and not the full amount for both.
they should be able to change the plan at best buy (we at radioshack can so i don't see why they couldn't) and in their activation system they can arrange for when to change the plan, immediately or at a future date
and my understanding is that the discount is assigned to the account not the plan so it should be safe even if you change rate plans