Starting this Friday, Sprint will offer customers the iPhone 6s for $1 per month. The deal is a direct challenge to T-Mobile, a company that is constantly trying to undercut competitors with low-priced smartphone packages.

The new low price is for those participating in Sprint’s upgrade program, ‘iPhone Forever.’

Sprint says the dollar-per-month deal will be available for the 16GB iPhone 6s with trade-in of an old iPhone 6. Consumers who trade in can also get the 64GB version for $5.77 each month, and the 128GB model for $10.53 a month.

Meanwhile, the 16GB 6s Plus will also require a trade-in and will cost $5 per month. Pricing goes up from there, with the 64GB and 128GB models costing $9.77 and $14.53 per month, respectively.

The announcement comes on the heels of a similar T-Mobile offer. Yesterday, the ‘uncarrier’ said consumers enrolled in its Jump program can get the 16GB iPhone 6s for $5 per month and no money down. Through the same program, consumers can have the 16GB 6s Plus for $9 per month. However, for 64GB and 128GB models, consumers will have to pay an upfront cost of $99-$199, depending on the phone.

The Sprint offer will be available until December 31, 2015.

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