Managing lots of little (sometimes contradictory) changes

Question

I work in a large company and most coding projects are fairly structured with a project plan and review process.

However, for existing support there are occasional periods where a department will need lots of tiny changes made to an existing app or site such the accounting department at the end of a fiscal year.

The problem is that they get incredibly busy and my team gets a slew of tiny emergency changes thrown at us. We need to be flexible enough to support their needs as they are real and provide a great deal of value to the company. On the other hand, given how crazy their environment is, they sometimes give us contradictory changes (change the text to 10pt, then the next day change it to 12pt).

Again, the changes are trivially tiny but they can suck up a developer's day given how frequent they are. I'd like to push back and set some fair limits for how we'll handle these requests going forward. Is there a best practice for handling these types of small changes? The department in question is far to busy to commit a lot more time to working with us. We also don't charge back so it's hard to communicate the problem to them. What's a good approach to resolving this?