My impression of this service is that Helio will be able to function on BOTH verizon and sprint networks, and at the time of call/use the phone service w/ the most stable signal will be the one used at that time. Is this correct? If so isnt it like having both sprint and verizon services? I am not following why either verizon or sprint would allow this and why anyone and everyone wouldnt go to Helio. What are the drawbacks to Helio?