There's also a very helpful Web site operated by the global GSM Association that provides GSM coverage maps and roaming information for anywhere in the world .
Once you have a subscription, most phones display a bar graph that shows you the type and strength of the wireless network signal. Your mobile phone will automatically select the best network based on your subscription and the networks available where you are.
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CAN'T FIND WIRELESS COVERAGE?
T-Mobile believes customers should choose the wireless service that's right for their individual needs. That's why T-Mobile makes its Personal Coverage Check (PCC) available online and at retail locations.
PCC displays signal coverage and varying degrees of signal strength for specific locations outdoors - down to the street level - enabling consumers to accurately judge whether T-Mobile's coverage is best for them. See T-Mobile website.
Sales representatives also use this coverage map at retail to provide the customer with a realistic view of coverage. If a customer's experience is different than noted in T-Mobile's Personal Coverage Check, Customer Care will work with the customer to troubleshoot the issue.