Sprint Corp announced a $1 per month plan for Apple Inc's new iPhone, upping the ante in a battle among top U.S. carriers to sign up customers ahead of the phone's launch on Friday. Sprint said on Thursday customers can get a 16 GB iPhone 6s for $1 per month and an iPhone 6s Plus for $5 a month, when trading in an iPhone 6. " is the day a lot of consumers choose who's going to be their carrier ... we wanted to make sure we have the best iPhone offer," Sprint's Chief Executive Officer Marcelo Claure said in an interview.