I call shenanigans.....
This in no way reflects my experience. Wherever I go in the country, never mind London, Vodafone coverage is pants for both data and voice. I usually carry a work phone (Vodafone) and a personal one (O2 via Tesco Mobile) and often have to use my personal one for work business due to Vodafone's total lack of decent coverage. Sure, it says you have a signal, but it doesn't work!