The program costs $22 per month, but Sprint is also offering a special promotion for a limited time. New and existing customers can trade in their current smartphone for an iPhone 6 and pay only $15 per month through the end of this year, when the price will return to the regular $22. However, if they receive their new upgrade before December 31, they can continue to pay $15 a month until their next one. This offer arrives right before Apple is expected to unveil its latest iPhone on September 9.

“They bring their iPhone, upgrade on the spot and away they go. It’s that simple,” Sprint wrote in the news release. Customers can get their upgrades from any Sprint retail store, the Sprint website, 1-800-Sprint-1, Best Buy, or Target.

The phone company is likely hoping that this offer will bring in more subscribers after it lost its number 3 spot in mobile subscriber rankings to T-Mobile earlier this month.