Call customer service and tell them what you want to do - if you and your Mom are on the same account, this should be doable without activating on your line first. If you are on different accounts, it likely will need to be activated on your line/account first, then swapped over to your Mom's.
Customer service can help in either case. (800-922-0204 from line not involved in the transaction, a landline or other phone).
Thank you,, how do I delete my question now?
No need to delete - someone else may have the same question, and as Ann154 said, they can learn from your question and the response. That's one of the cool things about the forum format - you can search and sometimes find an answer without having to post and wait for a reply!