Onecard — Fraud happening in Onecard they are not following RBI guidelines

Hi, I have done a transaction at a merchant using onecard and received the OTP with the exact same amount but after the transaction is completed I checked the history in Onecard application then the transaction amount was original transaction+1% service charge + GST.

How can they charge a service charge if I am not using their services from their application?
I have done the same type of transaction at same merchant using other national bank credit cards but they aren't charging a rupee then why onecard?

Is the RBI rules different for them?

I checked with their customer service and escalated as well but they are not refunding the additional amount.