The format-detection metatag defines wether phone numbers are detected automatically in iOS Safari or not.
Since this is blocking an acessibility-feature, it should only be used when there is no other workaround.
Read more about Apple's iOS meta-tags at Apple's official documentation.
<meta name="format-detection" content="telephone=no">
content can also be
telephone=yes, but the meta-tag is obsolete then, since the browser does this automatically.
In the WHATWG WikiUp to date: v2.3.3