Indian entrepreneur Anuj Gupta's start-up, GreenVan, is attracting global investor interest with its conversational AI software that allows users to book plumbing and other services through a WhatsApp interface. Gupta's own experience of struggling to find reliable tradespeople inspired him to create the "Amazon of Services." The UK market alone is estimated to be worth $120 billion, and Gupta plans to expand to the US and eventually India.