SERO is no longer, as it used to be "Sprint Employee Referral Offer".
It is now a totally different offer and now stands for "Separating Employee Retention Offer" (SERO) and the note says "This special offer is only available to separating employees and their Advantage Club subscribers".
Replacement offer to the OLD SERO is called "Everything Plus Referral Offer".
Refer to this
http://www.fatwallet.com/attachments..._sprintbis.pdf for clarification of what differers in these plans.