@lynchy95: Are you still able to send/receive texts, and receive inbound calls? Can you try switching off Wi-Fi, powering off your Galaxy S20, removing the SIM, powering back on, then inserting the SIM. Following these step, head to the Phone app > Tap the 3 dots > Settings, and check to see if Wi-Fi Calling is available to toggle on. To further troubleshoot the issue, head to Settings > Connections > Mobile Networks > Access Point Names > Tap the 3 dots in the top right > Reset To Default > Back > Network Operators > Select Automatically. If you're still unable to make outbound calls, you may wish to head to Settings > General Management > Reset > Reset Network Settings, although please be aware that this will reset all network settings, including Wi-Fi and Bluetooth.
I also recommend reaching out to your network provider to see if there are any issues with your account, or with the service in your area. If you have a Pay As You Go contract, make sure you have enough credit to use outbound network services.