My line is showing as Private Caller when I call out

The problem: When I make outgoing calls, the receiving party sees "Private Caller" or "Restricted " instead of my real phone number.

What I've tried:

· Checked all settings on my Samsung S21 (no Caller ID options available in the phone app)
· Spoke with a live agent on [DATE] who spent a long time troubleshooting
· Agent told me the issue was fixed and to restart my phone
· 1.5 hours later, after multiple restarts, the problem remains exactly the same