NEW YORK (AP) — Verizon, the once-unstoppable cellphone leader in the U.S., lost key wireless customers for the first time, even as it brought back unlimited data plans to counter smaller rivals. In the first three months of the year, Verizon lost 307,000 wireless subscribers who are billed each month, the more lucrative kind of wireless customer. MoffettNathanson Research says it’s the first-ever lost in that category, which covers phones, tablets, smartwatches and other connections.