What does a local SEO agency do that a marketing agency doesn't?
It works on the two surfaces that decide local search: your Google Business Profile and the pages of your own website. A general marketing agency usually works on neither.
Marketing agencies in Calgary sell brand, advertising, social and design, and they are frequently good at all of it. Local search is a narrower and less glamorous job: category fields, title tags, duplicate pages, service-area settings, and a page written every month for a question somebody typed.
The overlap is smaller than the shared vocabulary suggests, which is why 'we already have a marketing agency' and 'our local search is handled' are two separate statements. Ask yours when they last opened your Business Profile. The answer is informative either way.