Ok tobsw , that is what they offer me and i will accept but ( i have no other choice now ), i also need to make some changes on some dates of flights i have with them... why they can unilaterally change and i have costs ? I must accpet it, basically . Thanks
First, they are not changing it unilaterally: they are giving you the choice to accept the changes or full refund. We can argue whether airlines should be allowed schedule changes like this and don't offer any compensation to passengers (if they do it 2 weeks before schedule, then you are compensated).
There's always a risk of schedule changes booking flights so far in advance. Even though the majority of times the schedule changes are 5-15 min changes, sometimes they can be big. It is better to arrange other flights/connections closer to departure... so you consequential losses are minimised.
Anyway, hope you can arrange a cheap extra night in Medellín and sort out (with minimum financial impact) your other flights. More importantly, enjoy your trip!