Search engines record of every thing. If your listing shows a wrong number, not only will customers not reach you by phone, but google and other search engines save the record with the error. This creates an error message that stays with all the custodians of record (search engines) and your site will not rank highly when customers search for your type of service. Not only does this create a Citation error that will take tons of work to correct, but people will call the wrong number and obviously not reach you.
One thing worse than registry errors is "no record on file." If you search for your own business by the main listing phone number and you see an error message saying that the search engines can't find you, it means traffic to your listing will be small, if any.