The account number, which is different from your phone number, can be found on your bill. Enter it without the dash. Your PIN is typically the last 4 digits of your phone number. This information cannot be located on your bill, invoice, or online account. If you have a bundled bill, the account number will be a 12-digit number under your wireless account summary. Additionally, for bundled bills, you'll need to contact AT&T customer service to obtain the passcode, which will be a 4-digit PIN number provided by them. If you require further assistance, you can reach AT&T at 1-800-331-0500.