Calling up your customer after making a sale is a great way to keep them addicted to you and your business. A mechanic calls up his client the next day after servicing his car to ask how the car is doing. Boutique owner calls up a customer the next day to ask if the new shoes they bought wears nicely. A plumber calling up a home owner next day to confirm if everything he did is working perfectly. Same with tailors, electricians, computer engineers etc. A powerful customer retention strategy that costs so little. Use it.