How to complain politely

Excuse me

Look at this small dialogue:

Jane: Excuse me, I think you are sitting on my chair
Anna: Oh, I am sorry

Jane uses the words "excuse me" while she is complaining.

Look at these further examples:

You are waiting in the queue and someone is trying to get in front of you. You say:
Excuse me, but I was first.

You are watching TV and your mother comes in and switches the TV off. You say:
Excuse me, I wanted to watch that.

Sorry

Although we are using the word sorry we don't always mean to appologise.

Look at the dialogue again:

Jane: Excuse me, I think you are sitting on my chair.
Anna: I am sorry, but I don't think I am.

Anna disagrees with Jane. Although she uses the word "sorry", she says it is her chair, not Jane's.

Look at these further examples:

You are in the restaurant and the waiter brings you some food which you did not order. You say:
I am sorry, but I did not order that.

You are in the train and someone just put his music on very loudly. You say:
I am sorry, but I think this music is too loud.