Some customers prefer to complain in person while others would rather communicate in writing. For me, I think that complaining in person is better. Firstly, when you complain in person, that mean you're facing to the person who you don't like. When you're talking with them, may be you can understand the reason which they don't feel comfortable and make some mistakes. If they have some special reasons, we can understand and ignore to them. Second, when you complain in person, that mean that you'll not talk with the manager of them. Because when you talk with the their boss, maybe there's a reprehension between the manager and employee. That can make the employee was fired.