Immigration knows very well that they have no competition so they don't have to cater to your wishes. Especially for citizenship as they feel that citizenship should be important enough for you to jump through hoops and not make special requirements like for example move to another part of the country in the middle of your processing

You can give them a good reason why you could not attend your ceremony and ask for another date in Thunder Bay. You will have no idea when they will call you. Could be soon or could be a year from now. You are still not a citizen until you do the oath.
My advice, take a couple of days off work, fly to Ottawa and get it over with.