Gst on transportation charges/carriage

A company is a registered taxable person under GST and is engaged in selling the Edible oils Etc., some times it under takes the delivery of the sold goods through its own vehicles and charges the receipient of the goods separately for that and not in the original invoice of the goods. Now the question is whether the company is liable to GST on the carriage portion collected separately by it? Is there any specific exemption of such services? Please provide the relavant references also.