First of all, it is important to find out why customers are unhappy. Only after that you can come up with a solution. Many customers are unhappy because they normally expect one thing from a service but, unfortunately, they end up with another they did not want. This is reason enough to stay mad at your services. Admit it, you would also be upset and this is the reason why you should concern about it and try to fight it. Information can be the key to prevent such issues.
Remote support technicians tend to promise the world to clients in order for them to like them, love the service and recommend their services to their friends. However, it is important to know that promising something that is impossible to deliver can harm your business in the long run. For example, a customer has a huge problem on his computer and it will take days for you to fix it. You cannot promise him that you will solve his problem in a couple of minutes, because, the truth is, you really cannot. The answer to this situation is telling your customer that the problem will be fixed in two or three days. The truth.
Make sure you tell them that the quality of work will be worth the wait and that you will try to get it done sooner. Remember that if the problem cannot be really solved in less time, there is no company that will provide a faster service than yours, so no need to falsely raise the hopes of the client. What you can do, actually, is to promise a bigger deadline than needed. Then, delivery it the next day and you will look like a hero.
Last, but not least, never tell a customer you cannot solve their problem without even trying it. If you cannot solve it by yourself, ask for another remote support technician help.