How do I find my account number - Prepaid Accout

You do not port a number from one ATT account to another. To move a prepaid number to a “regular” ATT account, you must go to an ATT retail store, preferably a corporate store.

How do I find my account number - Prepaid Accout

Your daughter has a different prepaid account number than you do, all prepaid accounts have their own account number.  You can get account numbers AT&T from each individual phone. 

I need to my account number.

Not for this ⤵️

Wish to transfer my daughter's prepaid line (under my account as member)

You need to disconnect your daughter from your multiline Prepaid Plan by returning her line to individual.  Directions:

https://www.att.com/support/article/wireless/KM1117074/

to other regular AT&T account, how do I proceed?

Once your daughter's line has been converted back to individual, it is entirely on her to migrate to AT&T post paid in a corporate store

Do I remove her line from my prepaid account so that she can port her number to her new regular AT&T account?

Direction link ⬆️