WhatsApp link
A link that opens a chat with your shop, with the first message already typed.
How this works
The link is the wa.me address WhatsApp publishes: your number as digits, and the greeting encoded so accents and symbols arrive whole. It opens from a phone and from a computer, and it needs nothing of ours installed.
The zero people write in front of a number for calls inside the country is dropped. Left in, the link opens a chat with nobody, and it looks right, so nobody checks it.