I just received a text from VZW-FREE-MSG that I have to pay $50 in three days in order to keep my plan, despite the fact that I am on a $15/month plan with 300 minutes. I've only used 88 of those 300 minutes, too, so it's not that I went over.
I already have $20 on my account, since I switched from the $30/month to the $15/month plan a month or so ago.
The text I received:

My account (personal info. blocked out):

Why would I even pay $50 for a 300 minute plan?!!!!!!!