Hey ppl .. i have a bb 9500 for airtel india... i have loaded the apn settings. and the browsing is on

the issue is :

Below the network strength icon there is "edge" in small written ... all works well.

but sometimes it changes to "GSM" ... when that happens i have received complaints from ppl sayin that they have tried calling me and they receive a message sayin the fone is switched off ... nor do i receive any sms during tht period..

all i have to do is switch off and switch on the mobile... "edge" appears again ... and "aaall is well" till the time GSM appears again....

now i cant sit staring at the BB 24x7 to see whn edge turns to gsm... and then reset the fone ... all it is very inconvinient ...

please provide a solution... thnking u guys in advance