From the website of Fairphone: "The Fairphone 1 is an unlocked smartphone that has been developed for Europe. In all European countries, mobile network providers will support both 2G (GSM/EDGE) and 3G (UMTS/HSPA+). These are the specific frequencies: UMTS/HSPA+ (2100/900 MHz) and GSM/EDGE (850/900/1800/1900 MHz)."
It could be that in Columbia the frequencies of 3G is different from what the Fairphone uses for 3G.
Please check on your Fairphone which sim is getting the 3G. Is it your SIM1 or SIM2?
Go to System settings
Tap on ‘More’ in the section "WIRELESS & NETWORKS"
Tap on 'Mobile networks’
Tap on ‘3G service’ and see of your second sim is having the 3G-connection.
If not, tap on ‘Enable 3G’ and choose your second sim.