Relay number
Also: safe number, 0507 number
A phone number a platform allocates in front of a business's real line, so calls route through the platform rather than directly.
On Naver Place these carry the `0507` prefix, and between 37% and 87% of businesses publish only the relay depending on vertical. It is a privacy measure for the business and an attribution channel for the platform, and a dataset that does not flag it is a call list into a redirect.