I HAVE TWO YEARS of user data to confirm that when you can totally control the behaviour of your mobile phone, you can keep phone costs to one euro a week. Our grandparents are doing that with no data services.
You won't be able to constrain your running costs to five euro monthly (the average pay as you go charge my father-in-law incurs) unless you constrain email services totally to operations across wifi. And if you're a power texter or a Facebook addict, you have no hope of keeping your running costs so low. There's no Facebook in the lives of my in-laws because they prefer to deal with tightly-wrapped social collateral (i.e., viewing images and videos along with listening to occasional audio snippets on the handset). The Nokia E7 is a workhorse. I used it for several years as my daily phone--often getting more than two days between charges--and I still prefer its call handling and QWERTY keyboard over my Nokia Lumia. That's also the personal preference of the in-laws. The keyboard gives a greater sense of control over a touchscreen. The flip-up screen provides a tabletop focal point when using the phone on conference calls.
However, there is a major drawback when comparing the Nokia E7 over all other handsets my father-in-law has owned.