T-Mobile’s own prepaid homegrown mobile virtual network operator (MVNO), MetroPCS, has treats in store for All Hallows’ Eve. Starting October 24, it’s offering up to four lines of unlimited data for $100 — and a free phone to boot.

Here’s how to take advantage: New and existing subscribers who add at least one line of service get four additional lines of unlimited talk, text, and LTE data for $100 per month. But it gets even better: For every extra line they port in from another carrier, they get to choose a free smartphone from a list of midrange Samsung, LG, and Motorola handsets.

Here’s what’s available:

The deal comes out to a little more than half of what you’d pay on Cricket, Sprint’s prepaid brand ($100 vs. $180), but don’t ditch your current carrier just yet: There’s a catch or two. MetroPCS caps all videos streamed on its network to 480p (standard definition), and customers who use more than 35GB of data in a billing cycle are subject to reduced speeds. Tethering isn’t available on MetroPCS’s four-line promotional plan, and if one of the lines is deactivated, all lines lose the promotional rate.

If those restrictions don’t bother you and you don’t need unlimited data, MetroPCS’s standard-rate lines aren’t that bad of a deal. The carrier’s single-line, $30-per-month plan includes unlimited talk, text, and up to 2GB of 4G LTE data. You’re free to add multiple lines to a single plan (a two-line plan starts at $55 per month, and up to 4 lines is $25 per month for each additional line). And international calling and texting to over 75 countries starts at just $10 more per month.

With prices as competitive as those, it’s not surprising that MetroPCS was one of T-Mobile’s biggest revenue drivers over the past year. In the third quarter of 2017 alone, the MVNO added 226,000 new prepaid subscribers and committed to opening hundreds of new retail locations.