copy fields value to another field

When user registering on my site, they have to entry their phone number for auth (firebase).I have create the phone number field using buddypress’s xprofile plugin, the field named "phone". For some reason, I need to sync the Phone field to user_url field, I tried some plugin like SyncField ,BuddyPress to WordPress Full Sync to help, but the field cannot be sync without modify the content. Any idea to make it work?