Unlike a candidate in the running for a permanent role, you are not being interviewed as an individual. You are representing yourself as a business and the service you provide. This should not feel like a job interview; it is a business discussion.
You are not meeting the client to answer competency-based questions. Instead, you should be finding out what the client’s specific needs are, and what issues they have that requires a solution that your business can provide. When you talk about previous roles and situations, make sure they are entirely relevant to the company, the sector and the particular challenge at hand.