Does anyone out there have a different service provider for their iPad than for their phone(s)? I am an AT&T customer and have been long enough to have a grandfathered unlimited data plan for my iPhone 5. I am planning on getting an iPad 4, possibly with cellular data capability. If I do, I am thinking of getting a Verizon model instead of AT&T. Does anyone have any guidance/advice regarding this choice? Thanks in advance.