How to use my iphone as an iPod overseas without receiving any roaming charges?

Can I just put my phone into airplane mode to avoid roaming? Also would I be able to use Wi-Fi without any roaming fees?

Contact your provider and you can pay a fee to have the service when out of the country.

Airplane mode will avoid roaming fees, but you should just turn-off the data services while roaming. This way you'll be able to use your phone for the call display information of who's calling you. Also, let others know not to text you as you may get charged for receiving SMS messages while roaming. You may want to invest in an international roaming sim card to avoid high roaming and calling fees. Many times it's much cheaper to call back home from a local sim card service than using your own sim.