Internet provider that serves my area switches off the Internet at noon every day, and I have to contact the support team to make them re-enable the services for me. As I have a big kind heart, I don't aggressively act because I know that tech support is a front line that deals with all kinds of negativity and keep the line of fire.
There are only two types of customer contact centers out there. The first one is where the operators explain the product and teach how to use its features, the other one - constantly apologizes for the inconveniences. Talking with aggressive customers means stress and negativity, which is not easy to handle non-stop, and staff turnover in these contact centers is 120% in six months. You can train the soldiers just at the front line, but there cannot be great support when the product is bad.
One of my friends used to work in the online cosmetics shop's support team, and every time she was talking about her job, she rolled her eyes, saying - "Oh, poor customers! Never buy this bullshit!" That's it. This is a ship that is sinking – time to close the business, without doubts.
The employees should believe in the product, defend the brand and use the product themselves. During the onboarding training, educate the employees of the values and features of the product. Once every quarter, organize a seminar, meeting with product specialists, developers, and marketing professionals. The support staff knows what is happening with the product and can share the customers' reviews collected at the front line. If the employee is sure that the company offers a great product, he tries to help the customer, and, as a result, the customer support acts just like an additional sales department.