I use an ATT reseller called
H20 that has plans as cheap as $10 every 3 months. Customer service is not great but I haven't had to use that much. I have had them for almost 3 years. I went with the $100/year because I wanted some network connectivity but for just very limited phone the $10/3 months is a good deal.
My wife uses
PagePlus that is a reseller for Verizon. We actually use a reseller of the reseller called
Kitty Wireless because of some extra services. They have a terrible website but seems to work well, we have used them for a few months now. You can get by for $10/3 months there also. My wife uses that $12/month plan to get a little internet and more minutes.
Wife had a TracPhone for many years, worked fine but she wanted a smart phone, we can use out of contract smart phones on H20 and PagePlus so we switched.