Receive up to $504 promo credit ($180 w/Welcome Unlimited, $360 w/ 5G Start, or $504 w/5G Do More, 5G Play More, 5G Get More or One Unlimited for iPhone plan (Welcome Unlimited and One Unlimited for iPhone plans can't be mixed w/other Unlimited plans; all lines on the account req'd on respective plans)) when you add a new smartphone line with your own 4G/5G smartphone on an eligible postpaid plan between 2/10/23 and 4/5/23. Promo credit applied over 36 months; promo credits end if eligibility requirements are no longer met.
$699.99 (128 GB only) device payment purchase or full retail purchase w/ new smartphone line on One Unlimited for iPhone (all lines on account req'd on plan), 5G Start, 5G Do More, 5G Play More or 5G Get More plan req'd. Less $699.99 promo credit applied over 36 mos.; promo credit ends if eligibility req’s are no longer met; 0% APR.
I just tested with Verizon's Webmail, and you can. BUt adding one at a time.
Personally I use a client on my pc with no such limiatation