Iphone troubles

Hi,
I have been using my iPhone from america out in Belgium. So I'm using prepaid Proximus, with the international plan (where they don't charge extra to call international), and using the "surf 10" feature to add internet to my phone. For my iPad, I'm using base. It just seems like i find myself needing to refill my credit too often, and it's expensive! It also really pisses me off when I'm out and really need to make a phone call, and they inform me "i don't have a sufficient balance"

What is the best/cheapest plan in Belgium, Ive been around to Proximus, Mobistar, and Base, and have check out all of their plans. Does anyone have first hand information about these companies, (coverage, service, etc.. ?) I want to get a good cell provider, without paying an arm and a leg. I don't mind signing a contract, but don't want to find out after the fact that the company isn't a good one. I would also like my phone to work in other countries! Thanks!!