I was told I could "unlock" my phone to substitute sim card on international travel. Is this possible?

[theFantom]

A friend suggested a buy a local SIM card when I travel internationally next month. Is this truly possible? Does it void warranties or create other headaches?

Thanks!!

[bd94s10]

A friend of my travels internationally and buys a sim locally prior to leaving. You can do the same if you have a compatible device. He uses iPhone and it works great.

[mama23dogs]

Unless your phone is prepaid, it is not locked.   You do not void your warranty by using another carrier SIM card.  In many countries it’s cheaper to use local service.