The competition among mobile carriers continues to heat up. Sprint is introducing a limited-time offer that will give subscribers an unlimited data plan for up to five lines for $90 per month.

The details of the deal make things a little more complicated than the straight-forward way the offer is presented. Essentially, new subscribers will be able to sign up for a plan with unlimited text, talk, and data. The first line will cost $50 month.

The second line on the plan costs $40 per month. Lines three, four and five are free. All the lines will have unlimited data, though Sprint notes “Data depriortizatioan applies during times of congestion,” meaning they are subject to being throttled.

All the lines will also have to sign up for electronic billing and Sprint’s autopay program, which automatically withdraws money each month to cover the bill. The deal also applies to new accounts only, so customers making the switch to Sprint are the only ones who will benefit.

It’s also worth noting the pricing won’t last a lifetime. In fact, the promotional pricing goes away on March 31, 2018. From then on, the first line will cost $60 per month. The second line will still cost $40 per month, and lines three through five will cost $30 a piece.

The price jump after the first year might make the prospect of switching less appealing. For a family filling all five lines, the cost will jump from $90 per month to $190 per month as soon as the clock strikes midnight and it turns to April 1, 2018. Despite the date, the price difference in no joke.

Even with the built in increase come 2018, the Sprint offer remains competitive with other carriers. On AT&T, $190 per month gets subscribers five lines with just 16GB of data to split between the devices. Verizon offers a similar offer: five lines with 2GB per device, plus a shared pool of 16GB of data costs $190 per month. T-Mobile offers four lines with unlimited data for $160 per month.

Sprint’s super-competitive offering marks its latest attempt to make up ground on the other carriers. Once the third-largest carrier in the United States, Sprint has dropped behind T-Mobile in recent years and has struggled to find footing.

Now the company is playing a bit of catch up, as other carriers have created their own sweetheart deals to try to lure customers away from other carriers. In an age where there are no two year contract commitments and consumers are free to switch carriers at the drop of the dime, plans have become more competitive.