This is all very well and good if your client complies with your request. But what if they don't? Because of the few that do really kick up a stink, not a lot will do this. Aside from this, there are other issues to consider, such as literacy. For example, a lot of my clients are illiterate - some through lack of education, others due to language difficulties so a problem, should it arise, must be dealt with then and there. I also find that when a client is forced to put her complaint in writing that this tends to fuel the fire. We cannot afford to place such expectations on our clients if we want to continue to run a good business.
Good business means communicating with your clients, even when things get a little heated or have the potential to get messy. Just because a client gets angry doesn't mean you automatically hand her over to your insurer. A lot can be done with a few simple non-verbal communication techniques to throw water on a fiery situation.
One must look beyond the "I will not give a refund under any circumstances.." mantra. This is essentially saying that you are always right and the customer will always be wrong. Aside from the legal perspective which assigns you certain responsibilities that you must abide by when a complaint is placed, the basic tenet of good customer service means that you must emotionally detach from the situation, look at the client's point of view and judge the circumstances accordingly.
Personally, I would never allow my client automatic access to my insurer over something like this. And I would never allow a complaint to get to that stage unless I exhausted every avenue. This is part of my responsibility as a service provider.
Good customer service is not how we react to a complaint but how we respond to it. Good communication, not avoidance, is key here.