Cingular Wireless launched an online mapping tool that can be used to check coverage at a more detailed level than previous broad coverage maps provided. Cingular joins rival T-Mobile, which offers a similar detailed mapping service. Even the detailed maps have their limits because calls can fail in places that are shown as being thoroughly covered if a customer uses a phone from within certain parts of a building or house. The mapping improvement is one way Cingular hopes to enhance customer service. Sprint Nextel, is considering a mapping tool that will show street-level coverage, but it would be available only in retail stores. Verizon Wireless, the No. 2 rival to Cingular, doesn't plan to change its online maps, which offer broader guidance. In my opinion the next step in customer service is to acknowledge and comment on each of the nearly 20,000 complaints in our DeadCellZones.com database.