if i am in another country, will airplane mode enable me to use my phone without being charged for out of country use?

Yes. But no going on safari and all network enabled apps

like twitter, facebook, safari, etc.

Depends what you mean "use". If you want to make calls or use data over 3G/cellular: then no. The cel functions are off in airplane mode. If you want to use a free Wifi access point, you can turn on Wifi AFTER you have turned on airplane mode. You will not be charged for using Wifi (eg at a friends house etc.)