Hi @ PMM,
This issue is specific to Telstra SIMs, and has been reported to Google. It is difficult to fix or change on Samsung's side, but we will update devices immediately when Google resolves the issue.
In the meantime, you can try to see if these steps help as a temporary solution:
1. Settings > Biometrics and security > Other security settings > Device admin apps > Find My Device > disable
2. Settings > Apps > Google play services > More option > Uninstall updates
3. Settings > Google > Select question mark in upper right corner (or more > Help & feedback) > more > View in Google Play Store > Update
(or Chrome > open google.com > Search 'Play Services' > Select 'Play Services' update page > Install
4. Settings> Application > Google Play Services > Storage > Manage Storage > Clear cache, clear all data
5. Settings > Biometrics and security > Other security settings > Device admin apps > Find My Device > enable
Let me know if you have any problems with this or if you have any other questions.