Existing customers can get both services on same bill Existing T-Mobile customers will be able to have charges for unlimited monthly Wi-Fi access included in their voice services bills, the company said Thursday.The $19.95 bill for unlimited monthly access to T-Mobile’s network of hot spots at venues such as Starbucks coffee shops and Borders bookstores will appear alongside existing customers’ standard voice charges, said Bryan Zidar, a T-Mobile spokesman. Previously, T-Mobile’s Wi-Fi customers had to pay their Wi-Fi bills via credit card each month, whether or not they were also voice customers.The move is a logical step toward reducing customer churn, which affects all wireless carriers, said Dana Tardelli, research director at The Yankee Group in Boston. Nearly one of every three wireless customers leaves their provider each year, and the carriers are doing all they can to keep those existing customers from switching to other plans, he said. The greatest advantage of T-Mobile’s Wi-Fi service is its price, more so than the bundled billing service, Tardelli said. Compared to unlimited access plans for nationwide service from other vendors such as Boingo Wireless and Wayport, the T-Mobile plan is cheaper, and offers more hot spot locations. For noncustomers, T-Mobile charges $29.99 a month for unlimited access with a yearly contract, or $39.99 a month for just a one-month commitment to access the Internet at about 2,300 hot spots.Boingo offers an unlimited monthly plan for nationwide use at 1,200 hot spots for $49.95. Wayport charges $29.95 for a month’s worth of unlimited access if the customer signs a year-long contract, and $49.95 if the customer chooses to pay month to month for unlimited access to the company’s 535 hot spots at hotels and airports.Other wireless phone carriers plan to offer Wi-Fi services with their cellular voice and data services. AT&T Wireless’ GoPort plan costs $69.95 a month for unlimited access to Wayport’s network of hot spots, and Sprint has said it is working on rolling out a Wi-Fi service. T-Mobile, based in Bellevue, Wash., is a subsidiary of German cellular provider T-Mobile International which is owned by Deutsche Telekom. The company plans to introduce software improving the log-on experience of hot-spot users in the middle of this year, eventually working toward developing software and devices that allow users to roam between Wi-Fi networks and cellular wide-area networks, Zidar said. Technology Industry