Though Apple’s latest iPhones shipped with hardware support for eSIMs, U.S. carriers weren’t fully ready to support the feature until iOS 12.1.1 debuted in early December.¬†Now that Verizon and AT&T have introduced iPhone eSIM support, third-place U.S. carrier T-Mobile is joining the party — and using the opportunity to pitch its competitors’ customers to switch networks.

T-Mobile’s eSIM app¬†enables most unlocked iPhone XR, iPhone XS, or iPhone XS Max devices to instantly add a line of T-Mobile service. Three prepaid plans are offered as options, including a $30, 1,000-minute talk/2GB data plan valid for 21 days, a $40 monthly unlimited talk/10GB data plan, and a $70 monthly unlimited T-Mobile One talk and data plan. The first plan is aimed at tourists who want to quickly add U.S. service via eSIM while preserving their foreign physical SIM cards.

Once the plan is selected, a new T-Mobile phone number is displayed on screen and confirmed via email. Assuming both physical and electronic SIMs are in use at the same time, iOS 12.1.1 will then display a dual cellular signal strength indicator at the top right of the screen. Existing T-Mobile customers can use the SIMs’ separate phone numbers to divide work and personal calls, or effectively merge two phones into one.

What’s interesting is that T-Mobile is using the app as a chance to win over Verizon, AT&T, and Sprint customers as well. The app opens with T-Mobile’s pitch as “America’s fastest network,” and the company says that it’s giving rivals’ users the chance to “take the Un-carrier out for a test drive.” On average, T-Mobile’s network is slightly faster than Verizon’s, but well ahead of both AT&T and Sprint across many U.S. states, conceivably offering customers superior performance at lower prices.

When T-Mobile was first attempting to win over iPhone customers years ago, it offered a surprisingly effective test drive that sent¬†prospective customers full iPhones with complimentary data service, so people could see how the company’s signal strength and speeds held up where they lived and worked. With an unlocked phone and the eSIM app, that process could be as simple as issuing new customers promo codes for data service — assuming it wants to take that step.

The T-Mobile eSIM app is available now in the iOS App Store as a free download. It’s also listed as compatible with iPads and iPod touches, but for obvious reasons will be most useful on 2018 and later iPhones. An unlocked iPhone XR, iPhone XS, or iPhone XS Max sold outside of mainland China is required; for legal reasons, eSIMs are not included in Chinese iPhones.