Andes provided a uniquely terrible experience - they changed the return flight without informing us, we found out when we were checking in for the flight that the flight had been changed. We decided to go to the airport regardless, only to find that:
1) There wasn't a single employee there to help us
2) They weren't answering the phone
3) The flight they changed us to (next day) didn't exist
We had to buy last minute tickets with a different airline at double the cost, and they still haven't responded to our claim for a refund for the cancelled flight a month later.
Would recommend that you pay a little extra and use another airline.