Choose a methodology, develop a procedure and measure customer satisfaction.
In fact, the most important thing in CX-research is not the method, although it is certainly also very important. But it is much more important to work on improving the current performance once the results are in. "Work on bugs" in customer service should become one of the company's priority business processes, then the research itself has applied meaning. Interviewing customers just for the sake of interviewing is a meaningless waste of time for both the marketer and the respondent. So don't waste your work!