Verizon has recently come out with an attractive single line postpaid plan for basic phones. It may be a little more each month but you get full roaming and enough data for MMS to work properly. I have pasted the text from the Verizon web site below. I would go with this to be sure of functionality when needed.
Simply the basics, just for you.
Introducing the Single Basic Phone Plan, the new single-line plan that connects your basic phone to America’s most reliable network.
Unlimited Talk & Text, plus 500MB of data for $30/mo. Plus taxes and fees. No more counting minutes. All at a great price.