HTML tel links should NOT be wiped when Canvas scrubs edits.
virtually 100% of my students access their courses on their phones for most activities except completing assignments. There is no reason tel links should be wiped from pages, syllabi, assignments, etc. . . If they look at the syllabus to find the tech support number, they should be able to just click the link and make the call. Even desktop computers now often have a method for contacting a phone number.
Smartphones have been round for a few years now, so this wiping is obviously very old. It definitely needs to be updated for say. . . 2011 (It's currently 2017).