AT&T Wireless Services continues to struggle with a three-week-old glitch in an upgraded customer relationship management (CRM) software package, a company spokesman said Wednesday.The glitch affects new customer sign-ups in AT&T Wireless' service featuring Global System for Mobile communication (GSM) and General Packet Radio Services (GPRS), one option for its customers. GSM, widely used as a digital mobile phone system in Europe, is available to AT&T Wireless North American customers, but only about 3 million of the carrier's 22 million customers use it, said Mark Siegel, a spokesman for AT&T Wireless Services.The CRM software is preventing AT&T Wireless from signing up new GSM\/GPRS customers, Siegel said, but AT&T Wireless will offer credits to those customers. "We're going to try to do the right thing for customers affected by it," he added.The CRM software glitch will not affect most customers attempting to switch service to AT&T Wireless after wireless number portability rules went into effect Monday, Siegel added. Most of those customers are not signing up for the GSM service, and customer numbers this week have been "brisk" but not overwhelming, he said.The CRM software is reportedly from Siebel Systems, but AT&T Wireless has not confirmed that. Representatives of Siebel Systems did not immediately return a phone call asking for comment.Siegel declined to speculate when the glitch would be fixed. "As you know, in the software business, you're never through with anything," he said. "We're just moving as fast as we can."