In all honesty, you are better RINGING in as opposed to writing.
Call up your local Canx dept, and arrange canx of service, and arrange a date for pickup of your services.
Writting a letter takes to long to get processed in all honesty, we get letters off prospective new customers that were writted 1-2 months ago and for some reason take an age to get to us!
Call in, it'll save you time/effort and a lot of stress!!