General Problem
Especially in less developed countries (Eastern Europe, Africa, most of Asia), carriers and MVNOs often don't offer online top up. If you are in an Urban Area, it's not really a problem, but if you are on a roadtrip from Bukarest to Budapest (amiable alliteration, you might notice that it sucks big time

Great, so what do I do?
Well, if you don't want to be stuck without mobile credit in rural areas, you should try to get a top up online on one of the many different service providers. But be careful, they charge fees!

Here are the options
So, let's take a closer look:
  1. ezetop: many countries, but expensive like hell (up to 40% fee of the amount you top up)
  2. transferto: large coverage, but expensive as well (anyhow slightly cheaper than ezetop)
  3. fonmoney.com: currently only offering Romania, but they promise more countries to come soon (around 10%-15% fee)


Recommendation
If you are in Romania, give fonmoney.com a try. But always try to keep the top ups as low as possible and try to get them offline as soon as you are back in the city. It's simply cheaper.