How do we judge the quality of the customer service that is provided? Are there any general quality criteria?

thank you for inviting me.

I like simple - actions speak volumes. The best jude service quality is repeat business and acknowledging you and you interaction. This goes for both internal and external customers.

generally the quality of your service is evident in your actions. It is a "pracrice". A mind set. If you enjoy what you do and display your willingness to assist your customer - they will soon let you know about the quality of you customer service, in many different manners. Treat all the same and the respect you deliver will be rewarded over time.

you simply can't survey customers and expect "authentic honest " responses with set in store/enviroment question . If you want to serve customer it needs to be anonymous and they have to be motived to participate themselves....

1 - Repeat Sales / Business

2 - Customer feed back 

if you are looking for methods to check quality of your services please go through this article it will give you ideas about methods could be used for it

https://www.userlike.com/en/blog/measuring-service-quality

Agreed with Sir Joe Seychell's submission.

Thank you!

1. Company business workflow which grantee  segregated operational duties.
2. Identify customer problem systematic.
3. Service performance measures.
4. Close customer request by happy call.

Thanks for your question. 

Based on my experience, we can do VOC (survey) randomly or every after interaction. Monitor the results regularly. It can have3-5 questions focused on the interaction with customer.