What one has always noticed about phone calls is the receiver on the other end. Will he or she receive what you are saying, either generally speaking or of because this is of a specific matter. Will he or she process your information or feedback well-enough? If this is what, you are saying is it getting across.
Our initial hesitation of phone calls of a "take-care of business" matter have all these questions or at least a couple of them for instance could enter the mind. What it is, is really simple: we just want to be understood (both ends of the party now) and have the result end in a happy conversation. But if not a spectacular, courteous phone call, the conversation could finalize in a well appreciated, thanked, service-oriented phone call. Meaning both parties on either end can feel thankful.
With things being settled on your end of course, it may have just all went well. In fact, you may have made the service agent a better handler of phone calls. Just like him or her, you don't want things of your mishandled matter, making a need for this phone call to be an unpleasant outcome.
Like in any experience or shall we say things in "life to handle", these "to do" lists are essential. Think of it as people servicers or if not they are your daily chores. Use them wisely, keep them happy. If you can understand this, "you are people, even if you are not them."