Buy a phone in the USA

You need to ask your cellular provider in Columbia if the US version is supported there. But you should also be aware a phone purchased in the US will have NO WARRANTY in Columbia. If you buy a phone in the US and you need warranty support, you will need to bring it back to the US yourself. If you are wanting to buy a phone in the US because you think it will save you money, a warranty issue will eat any savings you think you'll get plus much much more.

It's best to buy the phone in the country you live and will use the phone.

On a final note. ONLY Apple sells fully unlocked phones. To use a phone purchased in the US, you will need to buy the phone from an Apple Store directly, pay cash for it and specify a fully unlocked phone.

Yes, but you will have to return to the USA if you need warranty service.