Howdy!
We are in the same unlimited grandfather data plan with Verizion and also have a 3g MiFi. I have also been considering the purchase of a new 4g MiFi. Hope this works out and would like to know the outcome. If not I wonder if you could just purchase a 4g phone or tablet and use it as a hotspot only. Even though we've only used it as data only from the gitgo for years it still has its on phone number assigned to it. We've never asked Verizon if we could move it from a data to a phone/tablet/data. What would the differance be?
"Happy Trails"
Chiefneon