Estimate the number of credit card users in India.

Focus on breaking down the problem into manageable components. Start by considering the total population of India and the percentage of the population that is likely to have access to banking services. Then, narrow it down further by estimating the percentage of bank account holders who are likely to own a credit card. Consider demographic factors such as urban versus rural populations, income levels, and the growth of digital payments. Use logical assumptions and data points to support your estimates, and be prepared to explain your reasoning clearly.