T-Mobile earlier today made good on its promise to introduce a feature in which customers can use just one phone number across all of their connected devices. It’s called Digits (not to be confused with Twitter’s Digits service) and here’s everything you need to know.

AT&T late last year announced a service called NumberSync that lets customers link their primary mobile number to all of their connected devices. T-Mobile Digits does the same but more importantly, it also allows multiple T-Mobile numbers to be used on a single device.

For example, you could use your personal smartphone to receive both work and personal calls, thus eliminating the need to haul around (and pay for) two devices. Each number carries its own voicemail and texts as well and when you call or text someone, it’ll show up on their end as you. It essentially eliminates the need for smartphones that support dual SIM cards.

It’s unclear if there’s a way to have only one device “ring” instead of having all of your linked devices ring at once. That would be ideal at certain times but not always.

Ever been in a situation where someone asks for your number but you really don’t want them to have your main number? With Digits, you can simply give them an alternate number that’s not your primary number.

T-Mobile says Digits prioritizes calls from your phone over other data so calls are more reliable with crystal clear HD voice quality and full mobility. This, the company says, is because Digits is your real wireless number with real wireless calling – not a “best-efforts” data connection like you’d get with over-the-top Internet calling services.

One shortcoming that has been identified is the fact that Digits lacks iMessage compatibility. As such, iPhone owners will need to disable iMessage and instead rely on standard texting, T-Mobile COO Mike Sievert tells PCMag.

The new service is available starting today (albeit in beta status) for postpaid customers. Interested parties will need to be running at least Android 5.0 or iOS 9 on their mobile device or Firefox or Chrome on their Mac or PC. The functionality is already baked into newer Samsung phones like the Note 5 and Galaxy S6 and will eventually be built natively into other devices.

Until then, T-Mobile says users can grab the Digits app from the App Store or Google Play. Interestingly enough, you can even use Digits on devices from other carriers like AT&T, Sprint or Verizon.

T-Mobile plans to launch Digits commercially early next year at which time it’ll begin charging for the option. How much, you ask? Well, T-Mobile isn’t saying right now short of noting that it’ll be cheaper than adding a new line to an account.