Reverse service is after the product (service) is sold, the company provides customers with services to realize the value of the product (service). According to the above definitions, which of the following is are not reverse services? ['A telecom operator launched a preferential activity of "send phone calls to send mobile phones".', 'An air conditioner manufacturer provides customers with free on-site repair services for life.', 'An online store can offer free returns and exchanges within 7 days after the sale of goods.', 'A car 4S shop provides customers with second-hand car valuation and transfer services.']