if you are in Panama City and want the flying option to Colombia, you have 3 major flight companies to use. Avianca, copa airlines and american airlines. among those it is important to know that though you should check price differences in any rate, avianca does not allow direct flights from outside b>Colombia to anywhere but Bogota, so if your first place you want to get to in colombia is caratagena, medellin or whatever else, you might be better with other airlines.
avianca also has a kinda limited variety of cities that they reach in south america. for example they dont have flights to cusco, only lima, and they dont operate in bolivia at all. while in copa airlines and american airlines you might find direct flights to where you need.
by the way, the avianca offices in Panama City are located in front of the hostel voyager. the other offices i am not sure.