The phone number exchange may be slightly visible. Here is one way to make the replacement of the telephone number with Search & Replace “invisible.” #

With CSS, it is possible to hide the search string and only then display the Call Tracking number after it has overlaid the search string.

See here for detailed instructions:
CSS as a way to hide the search text

What can I do if script or ad blockers are being used? #

There are cases in which the search string cannot be replaced by a call tracking phone number. Script and ad blockers sometimes prevent scripts from running on websites. Individual browsers now also have optional settings that protect against the perceived security risk in a similar way.

In this case, the transparent search string will remain transparent and website visitors will see no telephone number.

Solution #

Using the tag <noscript> means that the search string can be displayed if scripts are blocked. The search string will also be displayed in this case.