Remember, no phone service is iron clad. VoIP can often get a bad rap for it's quality - sometimes justified, many times not - but lets not forget how unreliable good old cell service can be. Why does t-Moblile always drop calls at the same precise spot on the downtown connector in Hotlanta and why do 1 in 5 calls find me pressing redial because i get that annoying 'call ended' beep beep? So here you go Sprint - put a nice big bill board message on the Atlanta downtown connector, right by that nice big Olympic torch, proclaiming "Dear T-mobile customer, i bet you've just lost your call, come join Sprint and talk clearly from this very spot".
Go make yourself be heard. Here's a good google mash up where you can make your good-signal bad-signal posts http://www.signalmap.com/