It's no doubt a VERY political process. They will likely not be interested in working with you unless you have a ton of users or will pay for the time they need

It's no doubt a VERY political process. They will likely not be interested in working with you unless you have a ton of users or will pay for the time they need to integrate with whatever system you build and even then I'm sure it'd be hard to convince them. I'm pretty convinced that the only way to have a phone that will work in EVERY country, for now, is to get a satellite phone which has a moderate up front cost and a comparatively significant marginal cost (per minute). Good luck though!