It is a lot of pain, but it seems the demonetization is going to make India a leader in m-financial services. Across the country, about 70,000 merchants a day are signing up for India’s best-selling mobile payments platform, Paytm, about 14 times as many as the daily average before the currency decision, said Vijay Shekhar Sharma, founder and chief executive of Paytm and One97 Communications, the start-up behind it. Since the large-currency ban, the number of daily transactions on Paytm has grown to nearly six million, an increase of 350 percent, and the service is adding half a million users each day, Mr. Sharma said. “Earlier, we were the innovator, now we are the mainstream,” he said.