Bharti Airtel has reduced the validity of its Rs 219 prepaid plan from 30 days to 28 days.The plan includes 3GB of data, unlimited voice calling, and 300 SMS with a daily cost of Rs 7.82.Airtel aims to increase its average revenue per user (ARPU) and has been vocal about raising tariffs in the industry.The company plans to reach an ARPU of Rs 300 in the short-term and the next major tariff hike is expected in 2026.