Phone and SMS QR codes
A phone QR can nudge the dialler with your number. Useful on service vans, field posters and support cards where typing a long number is awkward.
Use the international format when guests may roam (+ and country code).
SMS codes
SMS QR codes can open a draft to a number, sometimes with a suggested message (for keyword campaigns). Keep prefilled text short and clear.
Tell people what happens after they tap Send — surprise charges or spammy copy damage trust.
When a URL is better
If you need rich help content, prefer a URL QR to a mobile help page. Phone/SMS codes are for direct contact actions.