Know your client
Twice during my career, being a decision influencer evaluating the continued relationship between my business with a service provider, I have heard people that should know better make a rookie mistake; asking a question that makes it clear they have no idea what we actually do.
If you are scheduled to speak with a valued client, some very basic research is in order. Who are they? Where are they? What do they do? Where are they located. These are simple things to find out.
Not knowing the answers to these simple questions reflects a lack of care or concern about the client and does nothing to give them any confidence that you are capable or interested in resolving their issues.