When you request to have the 4-digt password sent to you, the password is only temporary in order to for you to access your prepaid account. You will have to go into your account a create a new password to use in the future.
To create your new password, you can follow these steps:
I still can't use the 4 digit password. I have to type in my 12 digit online password. I honestly don't know what's going on. I didn't have any trouble with AT&T up until January. I don't know if its just us prepaid customers or what. They have a whole log of bugs that needs attending to. I didn't accept his solution.