I guess I'm confused a bit. If you just mention their name on our website it's purpose is to attract people that want their Canon printer fixed, isn't that a advertising tool?
You can say on your site that you service Canon equipment. That is not a problem - or should not be, at any rate. It is impossible to guarantee that a trademark holder will not object even to legal uses of their trademark.
Most importantly, your use of the Canon trademark should not confuse consumers into thinking that you are something that you are not (e.g., an authorized Canon dealer). You cannot use the Canon trademark to deceive consumers. You cannot trade off the Canon trademark in a way that suggests Canon has some connection to your business if they don't, by advertising your business as a Canon business or implying that it is a Canon business.
In other words, the name of your business should not be "The Canon Repair Business" and you should not have a banner on your website that proclaims it is. You should not have a Canon domain name that confuses consumers into coming to your site expecting that you are an authorized Canon company. Allowable would be to have a business called, say, "Geilow01's Repair Business," and state on your site or in your advertising that your business services Canon equipment.
The purpose of trademarks is to distinguish one company's products and services from those of all others, to allow for consumers to know what they are getting when they purchase a product or service. When a consumer becomes confused as to the origin of the goods or services being offered, because one trademark too closely resembles that of another or one trademark is used in a way that confuses consumers as to the origin of the goods or services, that can lead to an infringement suit. And that is what you want to avoid.
For the best determiner of if you are using the Canon trademark properly and without (too much) legal risk, you can have your website personally reviewed by an IP attorney in your area.
Good luck, geilow01.