The important thing to note is that when you tether an Internet-capable device to your phone, you’re using the data that’s included with your monthly phone plan. This means that a plan with 25GB of high-speed data could have a combination of regular usage and tethering usage up to 25GB. If you use all of the included high-speed data in your plan before the end of your billing period, you’ll still be able to access the Internet, but it will be at a reduced speed.
If this happens, you can add more high-speed data by purchasing a Speed Pass.
Tethering is an included feature of the More Unlimited plan and is available as an additional feature on the Simple Unlimited plan.