Usually it is better to use the account number, but since this is a porting problem I will private message you a support number to call (this is for use in porting problems only). Check your private messages in a few minutes.
In Transfer Number page, where I am supposed to enter the Previous Account Number there is a TIP below the box that says "You'll need to provide your IMEI number. Account numbers are not accepted in this field."
My problem is the my original phone was destroyed, so I don't have access to the original IMEI only the pin (1856) to access my old account. My previous provider said the pin was all you needed to transfer my phone number over.
Use the PM app if you can for the entire signup process! During the signup process when are at the step where you are choosing a number you can select to port your number from another provider. You will have to provide them with the account number and the phone number from your previous provider. Keep the previous provider’s sim in your phone as the account has to be active and you must respond to a text authorizing the port. Once you lose signal on your old sim is the sign to put in your PM sim or turn on the eSIM and reboot your device.