Not true in my case, even I did a trx with my Infinia for a 2AC ticket few days back and its correct.
They charge 1%+GST by Smartbuy. I got a otp sms with 4725.75 but the charge I got in my statement is of 4781.45 (Additional 1.18% of 4725.75 which means 1%+GST by smartbuy who is aggregator here)