Service tax on used car sale

My client is a authorised used car dealer and the modus of operandi and the query is:-

Modus of operandi

Used Car Dealer purchase the used car from the customer

Used Car Dealer take a copy of invoice from the customer

Used Car Dealer take signature on the blank transfer form for RTO purpose

Used Car Dealer sell the used car to another customer

Used Car Dealer issue the invoice to the customer

Used Car Dealer charge vat @ 1.50% as per MP VAT ACT on the invoice

Used Car Dealer fill the customer name in RTO transfer form and get it transfer in the name of customer  whom Used Car Dealer sold the vehicle

As per service tax department

As per service tax department, service tax is payable under “Business Auxillary Services” if the vehicle is not transfer in the name of used car dealer and directly transfer the vehicle in the name of customer whom Used Car Dealer sold the used car.

As per service tax department, Service tax is payable on the surplus of the sales amount from the purchase amount after deducting VAT amount.

Query

Whether above service is taxable under the service tax, If taxable under which category and on which amount the service tax is payable?