Local SEO for heating and air company

We currently run the mobile advertising campaigns for a local HVAC company. They would like us to start a local seo campaign for them, we are knowledgable about citations, social signals, reviews, getting local links etc. but are at a loss for what to do about their on site seo.

They have offices in to cities, 20 miles apart and service the surround areas for each of those cities. Their website homepage has both office addresses and phone numbers listed...how will this affect their local seo how does one fix any issues pertaining to it?

Thank you for your help!

What I normally do in this type of situation is pick the main office, and create a landing page for the second location. If this is not an option, then I'll optimize each page with both locations, as long as it's only two physical locations. Any more than two, and you're getting into a soon-to-be mess without location specific landing pages. This has worked beautifully for me, as I have #1-#3 spots on Google for all of my local SEO clients.

why not making a own page for each branch ?