A couple of weeks ago you bought a gadget but it did not work. You phoned the shop, had a conversation with a manager there but no action was taken. Write a note to your friend describing the situation.
In your note:
I describe a problem with the gadget;
explained what happened when you phoned the shop;
say what you would like the manager to do;
ask if your friend has ever faced such a problem and ask him for advice.
I Write a complaint letter of 60-80 words.