I looked into Millenicom on Verizon and asked what the cost of exceeding the 20GB limit was. I was told that if you go over they simply shut you down until the next month.
If you don't think that you will ever need more than 20GB then Millenicom is a good solution but if you think you might go over some months it may not.
Millenicom does have an unlimited plan but it uses the Sprint network and is limited to 3G (as opposed to 4G). I had that plan a few years ago and hated it. Sprint's coverage (IMO) is terrible compared to Verizon and even though I had an unlimited plan, any month that I exceeded 20GB of data I would get an email from Millenicon chiding me for using more data than I should.
