Telecom regulator TRAI has approved hike in processing fee for all mobile recharge coupons or top-up vouchers priced above 20 rupees but has left it unchanged for the vouchers below that.Trai cleared the increase of 50 per cent in the charge through an amendment made to the Telecom Tariff Order, TTO after about two-and-half years.Trai said in TTO that the authority has decided to increase the ceiling on Processing Fee on Top up vouchers to 3 rupees from 2 rupees in respect of Top up vouchers having maximum retail price of 20 rupees and above . It said it will continue with the existing ceiling of 2 rupees in respect of top up vouchers having MRP of less than 20 rupees.This order will effect more than 90 per cent pre-paid users in the country.