ive read on numerous forums about how there is an innate problem with the voicemail indicator- that a blank text message is received when a new voicemail is left or when one is deleted. the phone doesn't process it correctly so the voicemail indicator just stays lit.
I have this problem as well with Cingular. I have talked with Cingular for hours on this and also contacted Nokia Europe(USA does not support the phone) The problem is with the US carriers. The notification is sent via SMS. The fix I got was to turn of SMS notification. But that left no VM notification at all. It also cured the phantom VM indicator problem. When I had the 6270, I would just automatically chack my VM if I missed a call. Guess its the price to pay to have an out of market phone.
I have since sold my 6270 and got an N80. Problem solved, permanently.