Cingular Quarterly Operating Profit Falls  NEW YORK (Reuters) - Mobile service provider Cingular  Wireless, which is buying AT T Wireless Services  Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AWE.N target=/stocks/quickinfo/fullquote"&gt;AWE.N&lt;/A&gt;,  said on Wednesday third-quarter operating profit fell on merger  expenses and increasing costs for signing up new customers.