Thank you for your letter about studying in Canada
I am writing to tell you how grateful I am for…
I would like to thank you most sincerely for…
I am writing to complain about the poor service at your dining-room.
I wish to make a complaint about…
I am writing to draw your attention to…
I am writing to you because I am unable to…
I am terribly sorry that…
I would like to express my apologies for not being able to…
I would like to obtain/request/seek/inquire some information about…
I am writing to ask if you can do me a favor.
I would like some detailed information on/about…