In the latest addition to its Un-carrier Unwrapped promotion, T-Mobile announced Thursday it is offering AT&T customers a bargain on the new iPhone as well as half off all EIP accessories when they make the switch.

Starting tomorrow through December 13, T-Mobile said AT&T customers can get a 128GB model of the new iPhone for the price of the 16GB model. AT&T customers who make the jump can also save up to half off T-Mobile’s financed in-store accessories, including smartwatches, Bluetooth speakers, headphones and Fitbit fitness trackers.

“I can already hear AT&T customers asking ‘What’s the catch?’ And I don’t blame them—because with AT&T there’s always a catch,” T-Mobile CEO John Legere said in a statement. “But that’s not us. And this is our way of showing long-suffering AT&T customers exactly how the Un-carrier gives you more without asking more from you – with a sweet memory upgrade on the world’s most famous smartphone – and half-off the best accessories. It’s our gift to you.”

The offer to AT&T subscribers is the third in T-Mobile’s Un-carrier Unwrapped promotion series, aimed at retaining existing customers and wooing those of the competition. Legere kicked off the series just before Thanksgiving by giving away three months of unlimited high speed data for all existing T-Mobile customers and followed with an announcement last week that T-Mobile would give Sprint customers a $200 credit for every line they switch. A promotion targeting Verizon customers is expected to be announced next week.

The offer to Sprint customers ends Sunday, December 6.

As with the Sprint news, T-Mobile investors reacted poorly to the latest promotion. As of 9:40 a.m., T-Mobile stocks were down about half of one percent.