Since I started using Cell phone, I have used Airtel, BPL & Vodafone Services. I found Vodafone the best out of the them. The biggest problem with Cell Phone Network Providers is the Coverage. If you compare Airtel, BPL & Vodafone in terms of Network Coverage, I found Vodafone has the best network in the market. Even while being in remote areas its network coverage is very good.
I have been using Vodafone since last 3 years and never had any problems with them. Many people have a misconcepton that they will be over charged in Post paid service (Billing system) which not the truth actually. I can say that as far as vodafone is concerned. I never had any billing issue with them in these 3 years. I mostly use internet to make my bill payments of vodafone as its very simple and convenient. I would definitely recommend vodafone as far as Mumbai is concerned.