Same for me, had my new 24 + delivered on 3rd, but still haven't received the return package for my old phone. I've used the upgrade program since my S20, and the return bag always arrived within a few days. I also used to get an email from klarna saying they'd be advised by Samsung I'd upgraded and would pause my repayments until Samsung advised the phone had been returned and they would clear the account
This year, I've moved to the new flex system and heard nothing since my new phone arrived. I'm assuming Klarna will be taking payment for my S23 next month, so I'll be paying for both phones as payments under Samsung finance start next month.