Are there alternatives to multi-line comment boxes in a contact form?

Hi! My company wants to do away with the multi-line comment box on our “contact us” web page. The concern is that people have been putting in uniquely identifiable data which, if accessed from the outside, would be a huge security issue. We have put text on the page asking people not to put in personal data, but as long as that text box sits there… Alternatively, if we don’t have that text box, how will we know what they want to ask us?