Can you actually reach the highest grades in the area of customer service through training?

Training and education are the basic foundation for success

yes, but we should have deviation towards the work too.

It Depends on the training plan that you put you have to include soft skills beside the technical skills such as communication skills - anger management - time management ......
etc through that you can reach the grade you are looking for

Certainly not, and the reason because the customer service needs as well as personal skills training because training alone is not enough

Highest level in customer service is not likely since service is continuous and dynamic.
Everyday is a time to show highest level the levels of which differ with customer requirements.
I think it is not possible to be highest but to maintain a progressive level of high customer service is possible

I think that training and experience is no doubt a key factor in that, but also the capacity of individuals have an impact in terms of abilities is not a single degree