The problem very well could have been on the other parties side. For example, if they had Bluetooth on and didn't realize it, they wouldn't hear you... in any case, it's definitely not normal for your phone to do that. Or if not Bluetooth related, it could still have been your friend e line that has the problem. If you had tried to call somebody entirely different and the same problem persisted, it would be a different situation.
Hopefully it doesn't happen to you again. Btw, congrats on your phone choice; the S20 is a great phone! 👍