As for training, it should be said that as long as there is a certain degree of professionalism, training is actually needed. Generally speaking, business knowledge related to an enterprise is trained within the enterprise, and skills are generally trained by external institutions. It is impossible to do it well without training. In other words, what you have learned is your own, and you will have more room for promotion in the enterprise in the future.
I know there is a Changda call in Nanchang University that specializes in call center skills training. You download Baidu.