A new pilot project by Citibank is enabling some Bronx residents to ?touch and go? by paying their subway fare with their cell phone.Thirty subway stations, including the 138th Street station in the Bronx, are participating in the test program. Citibank, MasterCard and Cingular Wireless customers can pay their fares by touching their cell phones to a special PayPass device that has been installed. Some residents say that while it may save time, they worry about the possibility of an invasion of privacy.Citibank says the trial period will last for about six months. It says the Nokia phones used for the pilot are equipped with radio frequency technology. The phones can be used like a credit card anywhere PayPass is accepted.