Cell Phones and SIM cards.
Been seeing a number of posts about this, and I figure I'd share my experience.
I knew nothing about the rules / laws here when I purchased a SIM card at Claro in Laureles (next to the Exito / mall) three months ago. I was paying so little attention to the process that I can't remember for sure, but they must've registered it correctly using my passport and whatever else they needed. I've had no problems adding credit since that point.
On the other hand, my wife went to Tigo and she's gone through Dante's Inferno trying to get it sorted. Her phone was locked, and ultimately she had to plead with and badger the guy at Tigo who sold her the SIM card to meet her at a government office etc etc etc. It took three appointments and two weeks to fix the issue.
Small sampling size so I wouldn't necessarily claim that Claro is better than Tigo. But if you're coming here and planning to stay or return, make sure it gets done right the first time.