Had a similar thing happen recently and now I have four vouchers for $470 each that are little use to me since I have no plans to fly Avianca in the coming year.

My best use of the vouchers will be to buy Lifemiles and redeem them on another Star Alliance airline. There are occasional Lifemiles sales with 140% bonuses which means buying miles for about 1.4 cents each. I should be able to convert the vouchers into about 130k miles.

I have not attempted to buy the miles yet. There is a post somewhere on FT that said this can not be done over the phone and must be in person at an Avianca office. I don't know if this is true or not.