This website, PaisaTours.com, does not offer any travel related services - the website's purpose is to advise independent travellers where to go and how to go there. It is relatively easy to book individual flights and hotels yourself by dealing directly with the airline or hotel you choose. However, if you don't speak Spanish, you may well find it simpler to deal with a travel agency, or tour operator. Here's some recommendations, and suggestions from me.
Recommended Tour Operators
Recommended tour operators are personal recommendations of mine. I am familiar with all of them, either because I have worked for them, worked with them or am very familiar with their brand name.
Journey Latin America - past employers of mine who arrange both tailormade and group tours to Colombia. Very good for booking domestic flights and airpasses too. Fully bonded tour operator - the UK's best Latin America specialist.
Eco Guias - a long established Colombian tour operator based in Bogota. They are, in fact, Journey Latin America's supplier. An upmarket and very reliable operator, Eco Guias can book tailormade or group tours all over Colombia.
Aviatur - are Colombia's big tour operator with branches all over the country. You'll often see offices at the major international airports. Reliable, though maybe lacking the personal touch as they're so big. This travel agency also offers outbound trips for Colombians travelling abroad, and their website seems to only be in Spanish.
Other Travel Agency Suggestions
These are only suggestions, travel agencies and tour operators that I have heard of and appear reliable with English language websites. You will probably find these smaller operators better value than those listed above. Do send me your feedback.
Colombian Travels - an Australian based tour operator that specializes in both tailormade and group tours to Colombia.
DiversiTours - a Colombian-British owned travel company, based in Medellin, who offer tailormade nature, culture and adventure tours throughout Colombia. You can book, and pay, online.
Mantaraya - a travel agency specializing in personalized packages to Colombia. Toll-free US phone number.
Colombia Tours Solutions - an agency specializing in medical tourism (plastic surgery, dentistry etc) but that also offer general travel services. Canadian & US toll free phone number.
You'll find a few extra suggestions in the separate section on group tours to Colombia.