AT&T has started a new offer on the newly released iPhones. The carrier is allowing buyers of iPhone 6S or iPhone 6S Plus to avail another iPhone for free.

Various Samsung smartphones such as the Galaxy Note 5, Galaxy Note 4 and Galaxy S6 have been available through buy-one-get-one-free offer on AT&T’s website. The iPhone 6S and 6S Plus smartphones are not listed on the offer page. However, a spokesperson from the carrier has revealed to 9 to 5 Mac that AT&T is also running the same offer for the iPhone 6S and 6S Plus smartphones.

In order to take advantage of the offer, customers are required to sign up for an AT&T Next plan and purchase the iPhone 6S or 6S Plus smartphone. The carrier will then provide a credit of $650 to the buyer. The credit offered by the carrier is equivalent to the cost of the iPhone 6S with 64 GB storage and the iPhone 6S Plus with 16 GB storage.

Buyers who opt for the AT&T Next 24 plan will have to make monthly payments of $21.67 for 30 months. Customers, who opt for the AT&T Next plan, will be required to pay $23.22 every month for 28 months. On both plans, customers will end up paying $650 at the end of the contract.

The $650 credit received by the customer can be used to purchase another iPhone 6S or 6S Plus handset. However, the new handset should be of higher storage capacity than the purchased smartphone. Customers are also required to pay for the difference of cost between the two iPhones.

The credit will start showing on the customers’ bill from the third billing cycle. Customers will also have to pay for additional charges like service charges and taxes. Only AT&T subscribers with good standing can qualify for the offer. The buy-one-get-one-free offer on the iPhone 6S and 6S Plus smartphones will expire on Dec. 31.