How to Change Your SIM Card When You Travel
Q: I'm traveling to Europe. Is there a cheap and easy way to continue using my cell phone while abroad?

Most phone companies have international calling plans, which allow users to make calls abroad. If you have enough foresight to update your plan before traveling and are willing to pay the roaming fees, this option allows you to maintain your contacts and avoid dealing with any cell-related hassles overseas.
If you neglect to update your plan, or if your provider does not offer an international option, you can still use your phone while traveling by switching out your American SIM card -- a thin chip that stores your phone's identity -- for a country-specific one.
Not all provider phones -- particularly Verizon's products -- have SIM cards. And, even if they have a card, most phones are electronically "locked," preventing you from switching the SIM card so that you maintain loyalty with your provider. Luckily, you can usually have the lock removed, allowing you to insert a foreign company's card.
After unlocking your phone, purchase a SIM card from a local provider so that you can pay local (cheaper) rates. On most phones, the SIM card is found underneath the battery. To insert the card, remove the battery and replace the American card for its European substitute. SIM cards come in multiple sizes, so before buying a card, make sure it fits your phone. After inserting the card your phone will have a new European identity and you will be charged accordingly.
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