Hope that fine print isn't too fine for the customer to read:
"Savings through March 31, 2018. After the promotional period is over, customers will pay the additional $10/month for first line, the second line remains at $40/month and each of lines 3-5 are $30/month – with AutoPay."
$90/month for 5 lines goes up to $190/month after a about a year. That's over a 110% increase in your monthly bill!