Received SMS notification: the package you mailed has not been signed, and you want me to call you back.

It's possible, because if your friend sends you something, he will definitely inform you that even if you don't sign for it, the postman will send it to you for you to sign for. If the goods can't be delivered, the postman or courier company will personally call you to pick them up at the post office without sending a text message. I don't think any courier company will be stingy enough to give up for the phone bill a few cents ago, hehe! Because I often shop online, I know the process better. If you don't understand anything, please ask me. I hope you don't fall for it.