IDEA: Hire a 3rd party to check on your company’s service personnel. Protect your reputation.
Hire a company or a consultant to follow up on your service provided to your customers by your service representatives. Instruct them to randomly call customers immediately after the service was provided to ensure that the customer was completely satisfied. Make sure to ask them if anything needs to be improved in the future and if so, please describe it for the company to evaluate. You want to encourage truthful answers and good feedback thus an unrelated third party can many times reveal problems and need for improvement that an internal person will feel reluctant to do.
Consider giving service performance rewards to those employees who consistently are praised by the customers. These are people you want to be happy and not leave for other employment.