In general, there are always coverage and interoperability issues with any cellular service. Anecdotally, individuals report that though they carefully select a wireless plan and phone, they often experience unacceptable volumes of dropped calls in areas of the country where they specifically told the salesperson they intend to travel frequently. Grrrr!When customers try to cancel or change their plan, they get hit with hefty early-cancellation fees or asked to invest in a completely new phone to remedy the problem - even though the phone and service package was sold to them as most appropriate for their needs.\u00a0 Grrrr again!In most industries, products that don't work as advertised can simply be returned. Often, though, they must be returned within 30 days. And with cellular service, you might not know within this time frame whether your "product" works or not. After all, you might not travel for a while and by the time you find out your coverage stinks, it could be too late.Also, roaming users are sometimes considered "second class" citizens. In other words, some carriers give priority to home users over roaming users, who experience dropped calls when the network is full.What to do? If wireless number portability, scheduled to take effect Nov. 24 in the top 100 U.S. cities, prompts you to change providers, try to protect yourself better in your new contract. Some of the carriers, for example, have handset trade-in or upgrade programs. This can be helpful when network upgrades to new protocols render existing phones obsolete.\u00a0For example, to maximize coverage if you are (or become) an AT&T Wireless, Cingular, or T-Mobile customer, consider investing in GAIT phones (the acronym stands for "GSM\/ANSI-136 Interoperability Team") for users who are the most widely traveled. With all the network upgrading going on from TDMA to GSM to GPRS to EDGE, a GAIT phone protects against obsolescence by working with any of these networks plus the AMPS analog cellular network, according to an AT&T Wireless spokesman.GAIT phones are made by Sony Ericsson and Nokia and are coming from Motorola and Siemens, if they aren't available already.