Shopify Store Collection Quickshop Button Function

There is a hover button in our current quickshop function that we need duplicated - currently when the mouse hovers over the item on the product collection page, it says 'EMAIL US' and when clicked on, the user's email client opens with corresponding email address in the TO section. Items get this hover button when tagged with a specific tag in the backend. Also, when the item is clicked, the individual item page has an 'EMAIL US' button instead of 'ADD TO CART'. This hover button needs to be duplicated on our website. We would like it to say 'CALL US' and when clicked, should call our phone number when the user is on their mobile. Additionally, the button should also show up on the individual item page instead of 'ADD TO CART'. **PLEASE NOTE THAT ALL PRICES ARE NOTED IN HONG KONG DOLLARS.