3.2. Complaining politely

There are a number of formulas used when complaining in English. It's important to remember that a direct complaint or criticism in English can sound rude or aggressive. It's better to mention a problem in an indirect manner.

How to complain in a polite way

 a. I'm sorry to have to say this but...
 b. I'm sorry to bother you, but...
 c. Maybe you forgot to...
 d. I think you might have forgotten to...
 e. Excuse me if I'm out of line, but...
 f. There may have been a misunderstanding about...
 g. Don't get me wrong, but I think we should...
 h. Excuse me, but there's a problem with...
 i. I'm afraid I have to make a complaint. ...
 j. I'm afraid there's a slight problem with...

Adapted from : http://esl.about.com/od/grammarstructures/a/f_complaints.htm

 How to accept, delay and reject a complaint

 a. Oh dear, I'm sorry about that.

 b. I wish it never happened.

 c. I'm so sorry. I didn't realize.
 d. I just don't know what to say.

 e. I suggest you leave it with us and we'll see what we can do.

 f. I'm afraid we can't help you at the moment. Could you leave your contact phone number? We'll contact you soon

 g. Well, I'm afraid there isn't much we can do about it actually.