Know before you go: AT&T introduces International Data Plan for iPhone

When traveling on the high seas outside the United States, it's probably best if you power-off your iPhone: Press and hold sleep/wake for about 5 seconds and then slide to power-off. If you must use your iPhone during travel and need access to a data plan, check out this AT&T iPhone world data plan that gives your 20MB for $25/month. Participating countries include Canada, China and Mexico. Overage costs you $0.005/KB and use outside those 29 countries costs $0.0195/KB.

Thanks to Darrel N.

You can use UIctl to unload -w com.apple.CommCenter. This disables both EDGE and phone calls until you load -w it back on and survives power cycling/reboots/locks. You can also pull your SIM, unlock your iPhone and, presumably, use local SIMs.