I have a simple cell phone plan. It's called Ben (http://www.ben.nl) and it's a subsidiary of T-mobile in the Netherlands that's historically (since the 90s) been the simple cell phone plan provider.
Here's what I pay: €3/month for 50 minutes or texts and €9.95 for unlimited data. If I go over, I pay a premium of €0.25 for each minute/text I go over. Simple.
It can be done!