It seems the contractor working in the mailroom has no clue, or he drank too much the prior night.
You should:
1. Call NSC. Hope the message gets to mailroom contractors so they won't return it again.
2. Sent again to NSC, with a colored sheet notice on the cover, saying "Read this and ask USCIS suprevisor before returning the application". Print the instructions from the website pertaining to your situation.
3. Document all this back and forth filing. Keep the evidence. In case you are late and H4 expires, CIS allows such laps due to extraordinary conditions beyond your control. Your situation clearly fits.