Dear Sir or Madam,
I am writing to complain about a mobile phone handset, which I bought in your shop last month (exactly 20th January 2014). I had already phoned your helpline, but the people did not help me and nothing changed.
The faulty mobile phone handset do not work properly - the screen is blank. It seem the on/off button is jammed. When I was explaining this your helpline, they did not respect my receipt and told me that this is my fault that the phone is out of order, but did not explain how I can fix this problem.
In this situation I must ask for an exchange of a product and I advise you to check how your helpline prosper.
I look forward to hearing from you.
Yours faithfully,
XYZ.