If you travel overseas, here are some ways to cut costs since international mobile calls can be pricey. If you replace the SIM card that came with your phone with a card that works in the country you are visiting, you get several benefits. First, you don't pay roaming charges for local in-country calls, although if you are calling back to your home country, you will pay international long distance charges. Second, if people in-country are trying to reach you, they don't pay for the international calls either. (Some of the networks overseas have the more enlightened method of calling party pays, but we won't go there for now.) You also don't use any minutes on your mobile phone account, which can be good if you have a limited number of minutes - when you travel, you don't think about all the time you are on calls. The trouble is if you are going to several different countries, then you need different SIMs and have to keep track of the numbers too. That gets onerous.
So one solution is to buy a SIM card from another vendor who has cheap international calling plans. Many of these offer lower per-minute rates no matter where you are. You don't have to sign a contract, the SIMs are about US$50, and you can add more minutes to your account easily over the Web and charge them to your credit card.
There is just one catch. Chances are, your mobile phone is locked to your carrier that you are currently using. This means if you try to take out your SIM card and replace it with another card, your phone won't work. You might be able to receive calls, but not make outgoing calls.
So how do you get your phone unlocked? You can call your current mobile carrier and ask for the unlock code. Depending on the carrier and your phone, you may be charged an unlocking fee. If all else fails, you can buy a new phone -- make sure its an unlocked phone.
Plan on taking a few weeks to negotiate all of these options so don't do this a few days before you have to leave the country. And you might want to bring along your current SIM card, just in case and so you can make calls while you are waiting in the airport to depart.