My friend gave me some advice regarding international travel and cell phones--Will this work for my phone?

She said, “Call your phone company a week before you leave and ask for an unlock code. Then when you get here you enter the number into your phone, which unlocks it and allows you to use any SIM card rather than just your own cell phone service. When you get here go to a locutorio and buy a $25 peso SIM card and some credit.”

I’m pretty sure my cellphone is already unlocked because I didn’t buy it from T-mobile. I bought it here. It’s that phone, exactly.

So, it is unlocked, and it does have a SIM card, but aren’t there some other considerations? I don’t know a whole lot about cellphone technology, but I know there’s like tri-band, quad-band, etc. Don’t those come into play here? Somebody give me some advice.

Thanks!