Virgin Making Mark Among Mobile Services  NEW YORK (Reuters) - When Virgin Group &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=VA.UL qtype=sym infotype=info qcat=news"&gt;VA.UL&lt;/A&gt; Chairman  Richard Branson put his brand on a U.S. mobile telephone  service two years ago, there appeared to be scant space for  newcomers to the crowded market.