classic story of the tail wagging the dog. treat the customer firmly or walk away. They need to define what it is exactly that they are trying to achieve. Ask the closing question 'What is it you are trying to achieve ?' then SHUT UP, the first person to speak will lose control of the situation. If they say something like the old cleaners were unreliable, ask them to define how they let them down so you know exactly how you can go about giving the customer the improvement they want (when they say unreliable they may just mean that when the cleaners turn up they ask them to do other jobs, thereby not allowing enough time to carry out their normal cleaning effectively). e.g. If the latter information were the case, we can ascertain that the problem lies with the customer and not the cleaners. See how it works?