Apple's GPS + Cellular Apple Watch is here, and I've gotten a ton of questions from our readers and various folks on Twitter in regards to how cellular data works on the Apple Watch. Here's a brief overview of everything you need to know.

How carrier plans work

Let's get this out of the way: If you want cellular phone calls or data on your Apple Watch, you're going to need to connect the Series 3 to your carrier. If you don't, and you bought a Series 3 GPS + Cellular model for a non-LTE reason, you'll never have to sign up for a plan if you don't want to: You'll still have every feature availalbe on the watch aside from Cellular connectivity.

How do carrier plans work on the watch?

Unlike Apple's a-la-carte iPad plans, a GPS + Cellular Apple Watch is intrinsically tied to its parent iPhone plan; this allows you to receive phone calls from the same number even if you're out and about. This means that you:

Have to have a phone plan that currently supports eSIM (the technology used to connect the watch's cellular service)

Need a phone plan that currently supports adding the Apple Watch

Can't sign up for a different carrier on your watch than on your iPhone

In practice, this is pretty simple: When you set up cellular data on your Apple Watch, you'll be redirected to your current iPhone carrier's portal for Apple Watch, where you can add on a ~$10/month plan based on your carrier and region. There's no option for picking your own carrier like the Apple SIM, so you can't hack your way around your provider offering support for another LTE watch but not Apple's own.

What does LTE data cost on the iPhone?

Most providers are actually letting you share your iPhone's data plan for free; the only cost is instead a ~$5-$10/month "device fee" that covers infrastructure. It's a bit of a rip-off in terms of pricing — though, coming from cellular carriers, what else is new? — but there's currently no other option if you want to use LTE on your smartwatch.

Do I have to sign up for cellular data when I buy the watch?

Nope. When you first set up an Apple Watch with cellular support out of the box, you'll be asked whether you'd like to add it to your current cell plan; if you say no, you can set it up later at any time through the Watch app on your iPhone.

Will carriers lock Apple's eSIM to their network?

Not that we've heard, but it's best to check with your carrier.

Can I switch to a different iPhone plan (and thus, Apple Watch plan) at will?

As long as you can get out of your carrier contract, absolutely.

Can I cancel my Apple Watch plan at will if I'm not using it?

Depends on what your carrier demands, but you should be able to; in the U.S., all Apple Watch plans are month-to-month.

What if I move to a different state and change my cellular service provider? What about a different country?

As long as your new cellular company supports the same LTE bands as the current watch model you own along with an Apple Watch plan, you should be able to set up a new cellular account and add your watch to it on your new carrier. (You'll have to put in your new carrier's SIM into your iPhone before switching plans, however.)

For example, if you live in the United States and use AT&T but plan on moving to Canada and using Bell, you can cancel your AT&T phone and watch plan (or put them on hold), sign up for Bell on your iPhone, and add a Bell add-on plan for your watch.

How to roam with your Apple Watch and use LTE data in a foreign country

If you move to a country that uses a different subset of LTE bands — and, as such, requires a different kind of Apple Watch — then you'll have to purchase a new model for your new country.

How many LTE Apple Watch models can I have paired to one iPhone?

This entirely depends on your carrier, but generally, you can pair more than one if you really have a hankering to do so. AT&T, for instance, allows up to 5 smartwatches to share the same iPhone number on a single plan.

Can I have multiple LTE plans active on the Apple Watch?

While you can certainly pay for multiple LTE plans on Apple Watch, the eSIM can only relay one carrier at a time. For example, if you have an AT&T personal plan and a Verizon corporate plan, you'd have to go to the Watch app and switch your cellular preferences every time you swapped SIM cards — it doesn't happen automatically. If you need to, here's how to do that:

Open the Watch app from your home screen. Tap on the My Watch tab. Select the Cellular option Tap the Info button. Tap Remove [carrier] Plan to untie your Apple Watch's eSIM from your current wireless provider. Keep in mind: This won't cancel your plan; you'll have to go to your carrier directly if you'd like to do that. It's the equivalent of taking out a SIM card to add a new one. Switch the SIM cards in your iPhone between your current carrier and your second carrier. Confirm that you can access the internet with your new SIM card. Open the Watch app. Tap on the My Watch tab. Select the Cellular option. Tap Set Up Cellular to reconnect your watch plan with your other carrier.

How do I cancel a cellular plan?

Decided to ditch cellular data on your Apple Watch? Unfortunately, there's only one way to remove a plan permanently: Get in contact with your carrier.

Apple will let you remove the plan in question from the Watch app (via My Watch > Cellular > Tapping on the Info button), but that doesn't cancel your service: It's the equivalent of removing a SIM card from your iPhone. Removing a plan during the unpair process does the same thing.

Instead, if you wish to cancel, you'll have to either call or chat with your provider. I ended up using AT&T's online chat service to cancel my Watch plan:

Sign in to your AT&T account from att.com. Go to AT&T's Wireless contact portal. Click on the Chat available button to open a support chat.

Why can't I roam with Series 3?

Essentially, the roaming limitation comes down to two issues: space, and battery life. The Apple Watch Series 3 has very little room with which to fill LTE bands, and as such, each model has a very limited number of bands that it supports; there are currently six different models (three in 38mm, three in 42mm) for the 10 countries that currently support Apple Watch.