Cell phones of mobile telephony major, Airtel, in Hyderabad went silent since 6 a.m. on Saturday morning with what was termed a systemic failure of its network. Till around noon, the situation was the same and no Airtel mobile could be accessed. Enquiries revealed that Airtel was doing some system integration and upgrades on the network that includes slightly over 2,500 cell sites in and around Hyderabad,...