For this first task I would need at least two people, the first one to write a letter of complaint (as a costumer) and the second one to reply (as the personal working in a travel agency). Imagine that a couple of just married have just returned for their honeymoon. They have planed one of the most luxurious romantic routes around the world and most of the booked products failed or would not follow their expectations.
To have a more clear idea on hoy to write a letter like this, here you are some links for you to practice and learn a little bit more:
http://www.google.es/search?q=letters+of+complaint&hl=es&client=firefox-a&hs=F6H&rls=org.mozilla:es-ES:official&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=7Es6T-C-ENS3hAey-cmcCg&ved=0CEMQsAQ&biw=1064&bih=875 (different images to know more about the structure of a well done letter of complaint)
Remember to use the comments option to this activity. Don't forget to peer-review your work after writing both letter.