Here are some photos I took partly for purpose of proof, and partly for Project 366, but it occurred to me that they would act as a springboard for an interesting lesson or two. I am just going to suggest a few possibilities, but the way the lesson will flow depends on your students and you.
Conditionals (If I could afford it... If my purchase arrived like this... If they had packed it properly...)
bear (the cost)
I would appreciate it if...
I would be grateful if you could...
Would it be possible for me to...
I'm sorry to hear that...
Regarding the damaged item...
Under these circumstances...
If you would prefer to return the item...
We look forward to hearing from you soon.
Oral discussion on topics (go to Index File, ctrl+F, and search on "speaking")
Writing (complaint, request for refund, negotiation for discount)
Role-play (telephone conversation, forum, chat)
Webquests (assign a product [and a budget] and students purchase it: discuss the whys and wherefores later)
Those are just a sample of what could come up in such a lesson. If you have further ideas, you might like to share them here. If you need further spoon-feeding, I'll be here!