Vodaone's network is very good in Kolkata too...That's why I have been using both AirTel & Vodafone in my dual-sim phone...After AirTel, Vodafone is my 2nd choice of network...But Vodafone's customer care sucks big time...Even on FB & twitter they always send copy-pasted robotic replies without even reading the comments...All of these are good until you need to call customer care & when you will try to explain a technical issue to them, you will understand that none of these customer care people knows nothing about the technicalities of their own system...Our questions are always like "out of syllabus" questions for them...