Hi @Will240
Firstly, you are posting in a community forum of hosts and guests not monitored by Airbnb. If you want to speak to Airbnb best to give them a call or post on their social media.
Guests shouldn't be able to make a request if your dates are blocked, but may have made an inquiry (have a look at Airbnb Help Centre for details of how both work.
If it's an enquiry just message back and say the dates are unavailable on your calendar so you won't be able to accommodate them. You don't need to do anything else.