Bill Protection allows customers to use more than 6 GB without breaking the bank.

Customers will still be charged $10/GB until they hit the 6 GB threshold.

Some customers may be slowed down once they use 15 GB, but can pay $10/GB to opt out of slowdowns.

The theory behind Project Fi has always been simple: pay for what you use. The MVNO already offers unlimited talk and text for $20, plus $10 per gigabyte of data after that. If you pay for data you don’t use, you get a refund. Simple, right?

Fi has never offered unlimited data plans like other carriers, but a new program is changing that. Its called Bill Protection, and it allows users on Project Fi to use more data without breaking the bank.

Editor's Pick Google is making it easier for people to pay their Project Fi group plan bills If you are on a family plan or group plan with your wireless carrier, sometimes you have to ask everyone else on the plan to pay his or her share of the bill. Previously, group …

Here’s how it works: you’ll still pay $20 for talk and text and $10/GB for up to 6 GB of data. Once you hit 6 GB, Bill Protection kicks in and Project Fi stops charging you for the data you use after that. That means an individual line caps at $80/mo, but family plans get an even better deal. Bill Protection kicks in at 10 GB for plans with two lines, 12 GB for three lines, and 14 GB for four lines.

As with all unlimited data plans, there is a catch. Customers who use more than 15 GB of data in a month could have their speeds slowed down. Google says that this 15 GB soft cap would affect less than 1% of current Project Fi members, but that number might grow once you no longer have to pay $150 to hit the threshold. If you want to opt out of the slower speeds, you can pay $10/GB for your individual data usage above 15 GB.

Bill Protection is rolling out today and customers will see the change reflected on their next bill. It includes international data and applies to data-only plans for laptops and tablets as well. Google set up a calculator to see exactly how much you can save each month. Hit the button below to check it out.