Sprint aims to undercut T-Mobile with $1-per-month iPhone deal

Watch out, T-Mobile. Sprint is aiming to outmaneuver you in the battle to win over Apple iPhone 6S customers.

On Thursday, Sprint announced a new deal in which customers who trade in their existing iPhone 6 can score a 16-gigabyte iPhone 6S by paying $1 a month or a 16GB iPhone 6s Plus for $5 a month. Available for an unspecificed "limited time only" (no end date has been announced), the new offer is part of Sprint's iPhone Forever program, which lets new or existing customers eligible for a new phone get the latest iPhone as soon as it rolls out.

The new deal is Sprint's way of trying to top rival T-Mobile, which on Wednesday unveiled its own effort to score more customers eager to buy the new iPhone 6s or iPhone 6S Plus. T-Mobile's offer, which is part of its Jump On Demand Leasing program, asks customers to pay $5 a month for a 16GB iPhone 6S or $9 a month for a 16GB iPhone 6S Plus in exchange for trading in an iPhone 6 or 6 Plus.

T-Mobile and Sprint have been trying to outdo each other through one promotion after another, now taking advantage of the debut of Apple's latest iPhones.

T-Mobile, which passed Sprint as the No. 3 carrier in the nation last month, has been particularly aggressive in aiming new deals at customers willing to pay retail price for non-subsidized phones but who want to save money on the monthly installment plans. Sprint is trying hard to regain its position as the third biggest carrier in the nation. So as soon as T-Mobile cooks up a new deal, Sprint tries to beat it with something more enticing.

"Once again, it is clear that the best place to get the new iPhone 6s and iPhone 6s Plus is Sprint," Sprint CEO Marcelo Claure said in a statement. "New and existing customers who trade in their current iPhone 6 can now get a device for only $1/month, making it the best way to get the iPhone -- and a yearly upgrade is included in this charge."

So how does the new Sprint plan work?

Assuming you opted for the 16GB iPhone 6S, you'd pay the $1 per month for a total of 21 months. After those 21 months were up, you'd have three options, a Sprint spokeswoman said:

• You could continue to keep the phone, but the rate would revert to $22 per month. (The lease reverts to the standard lease rate for the 16GB iPhone 6S with iPhone Forever, which is $22.)
• You could buy the phone once the lease ended. (You'd owe $187, the standard purchase option for the 16GB iPhone 6S.)
• You could trade in your phone for the newest iPhone. (The $1-per-month lease for your iPhone 6S would close, and a new lease agreement would be set up for the new iPhone based on the current lease rate at that time.)

The new plans from both T-Mobile and Sprint do have some caveats, though.

Sprint's $1-per-month and the $5-per-month deals apply only if you trade in an iPhone 6 or iPhone 6S Plus. Trade in the iPhone 5S, for example, and the prices jump to $10 a month for a 16GB iPhone 6s and $14 a month for the 16GB iPhone 6s Plus. The monthly price goes higher if you trade in other types of phones. Through December 31 of this year, customers who jump ship to Sprint from another carrier or existing Sprint subscribers who are eligible to upgrade and trade in any other smartphone will get a promotional rate of $15 per month on a 16GB iPhone 6s, normally $22 a month without a trade-in.

Likewise, T-Mobile's monthly prices are higher if you trade in a smartphone other than an iPhone 6 or 6 Plus. You'll pay $10 a month for a 16GB iPhone 6S if you trade in an iPhone 5s, Samsung Galaxy Note 4 or Samsung Galaxy Note Edge, and $15 a month if you trade in other phones, such as an iPhone 5, iPhone 5c, Galaxy S4, Galaxy S3, HTC M8 or Motorola Droid Turbo.

And though Sprint's $1-per-month and T-Mobile's $5-per-month deals sound tempting, remember that you'll be buying an iPhone with just 16GB of storage. That's not a huge amount these days when you consider all the apps, music, videos and other content you'll probably want to store.

Under Sprint's plan, you'd pay $5.77 per month for the 64GB iPhone 6S and $10.53 a month for the 128GB version if you trade in iPhone 6. And you if want a 6S Plus, you'll pay $9.77 per month for the 64GB edition and $14.53 a month for the 128GB flavor, again with the trade in of an iPhone 6.

The mobile phone industry is undergoing a shift. In the past, customers typically paid a subsidized price for their smartphones under a contract that restricted them to a new phone every two years. Now, all four of the major US carriers are either requiring or encouraging consumers to pay the full retail price for a phone and giving them the option to upgrade to a new one more frequently. Apple has even set itself up as a rival by offering an annual upgrade in which buyers can pay off an iPhone for a certain amount each month in exchange for the option of buying next year's model.

Sprint's new plan starts Friday when the iPhones 6S and 6S Plus go on sale in the US.

Update, 2:30 p.m. PT: Adds details of Sprint plan.