If they are a Shopify expert or Shopify partner, then they are bound to Shopify terms of service, so you can open a case with Shopify support if they are not replying to your messages in a reasonable time. 3 business days with no reply is a long time in my opinion, 1 business day is pretty standard for communications on paid projects.
Founder of
Speed Boostr (Shopify optimization experts, theme customization, custom app development).
Creator of
Shopify Analyzer (first performance analysis tool for Shopify sites, free for the Shopify community).
Creator of
Order Automator (auto tag orders and customers + auto fulfill orders + email notifications).
Creator of
Theme Scientist (A/B testing app) and
Tip Jar (add a tip button to your store).
