Can you clarify? Are you speaking about the Airbnb Guest Service Fee and sometimes it's the split fee and sometimes your paying the whole amount (Simplified Pricing)?
Which Listings are you referring to? Can you post the URL to the listings?
If you are using a Channel Manager to manage all your listings, then the Airbnb commission is automatically switched to 15% + VAT and the host cannot choose to be with the split commission fee of 3%+VAT.