The courier company can change this number. Find the login name he registered at the time, log in, modify the contact information, and remove or change the mobile phone number.

They may have forgotten their password. There are password recovery methods behind the login box.

If it doesn't work, let them call Alibaba's customer service, they can also help to recover the password. Be sure to let the registered person call the customer service himself. I hope it helps you, and I wish you all the best!