There are Internet services that offer free e-mail addresses to consumers who, in return, must wade through on-screen advertising. Now, a company in Canada wants to offer free telephone calls--to consumers who agree to sit through a short advertisement. Montreal-based Gratuitel Communications Inc. promises "absolutely free" telephone calls to anywhere in Canada or the United States. Consumers would call a toll-free access number and listen to a 20-second advertisement before being connected to their long-distance number. The only catch so far? No advertisers have agreed to sign on, and company officials describe the recruiting process as "very slow."