Something like this would be appropriate.
Dear Sir or Madam (find out the name if you can)
I am writing to express my interest in the Switchboard/Receptionist (Casual) position at the Chilliwack Community Police Office as advertised on www.gov.chilliwack.bc.ca . I would like to be considered for this position.
In my previous position with the Canadian Superstore I have gained much valuable experience in dealing with members of the public over the telephone. Since leaving Superstore I have not only dealt with customers on the telephone but also in face to face situations too.
I perform very well in both individually and in a team environment. I consider myself to be diligent and thorough in my work.
In addition to the above I also have a great deal of experience in using computer software such as Microsoft Word and Microsoft Excel. I completed a typing course from UCFV in 2002 with 68wpm and an accuracy of 90%.
For these reasons I believe I would be an asset to the RCMP. I have enclosed my resume which provides additional details of my education and work history. Should you require any further information please do not hesitate to contact me. I can be reached at .... or you can call me on ... at ...(times/days)
I look forward to hearing from you.
Yours faithfully (Sincerely yours - if you know and use the name of the person you are writing to)