With Facebook hoping to get the Reserve Bank of India’s (RBI’s) permission for WhatsApp Pay soon, the company is bracing itself up to take on its rivals Google Pay, Walmart’s PhonePe, Alibaba-backed Paytm, and Amazon Pay in the growing UPI-based digital payments market. According to industry estimates, the biggest player is Google Pay with over a 40 per cent market share, closely followed by PhonePe. Facebook, according to sources, has complied with the RBI’s rules on data localisation. This, experts say, was a key reason for the delay in getting the green.