Write a letter complaining about faulty goods.

Dear Sirs,

This is to state that on (date), I bought double glazing for (amount) from the (name of store). However, I am sorry to inform you that the double glazing is faulty, due to which the bathroom window do not close properly, and also the seals on the lounge windows have failed.

On an earlier occassion too I complained about the matter to your store, as a result you sent someone to look at the problem but I have heard nothing since. I wish to claim a free repair/replacement from you. Kindly respond to my complaint within 5 days. 

Yours faithfully,