None, IMO. You can call your carrier, for $10.00 a day international plan is unlimited data and phone use. You only get charged if you use it. Ours through ATT always stays on our plan. Some might say that’s too much, but for us it works and it’s easy. To be honest, as advanced as phones are today with all the apps, every time this conversation comes up it really amazes me. Keep it simple, call your carrier, add the plan, and just use your phone, this is soo easy.