Rcm liability if supplier pay freight on behalf of customer

RCM means the Recipient of service should discharge tax to the government. In this case, you are the service recipient and you are liable to discharge GST irrespective of who paid the amount to transporter.

RCM liability needs to be paid by the recipient of service. In this case even though the supplier has paid the freight amount but if the supplier is the recipient of services of GTA then he need to pay Reverse Charge Mechanism (RCM) under GST