In Colombia I bought a TIGO SIM card for 10,000 pesos (US$ 5.00) which gave me free incoming calls, messaging for about 50 cents to foreign numbers and reasonable rates to other TIGO subscribers. Calling out is very expensive and I cleaned out my account after less than a minute. Vouchers are available everywhere.
There is a also Movistar. Best to go to their websites to check them out
www.tigo.com.co and
www.movistar.com.co
I have a Motorola V3 and all the SIM cards should work
Wolf