Have you ever broken company rules, or payment terms, to make a customer happy?

Breaking the rules, and bending them, CAN be different from each other. Often, organizations are okay with you bending the rules to keep a customer happy. You need to know your audience, though! If the company is very stringent when it comes to their policies and procedures, then approach this question with caution. If the organization is well known for being flexible, then you can indeed be more free with your answer.

"My current company is pretty strict with their policies, so I do not bend to make a customer happy, but I will escalate the issue to someone who has the seniority to decide that. I agree with your organization that it's important to offer some flex on policy, within reason of course."