Cost added for booking 2nd bedroom

[Raymonde22]

I advertise for one bedroom in  2 bedrooms apartment   Sometimes guests want the 2nd room to rent at extra cost.  . If guests book the 2 rooms,  airbnb doesn’t have a system to add  that extra cost. They said I should do another listing for 2nd bedroom but then I let that room only if 2  guests or if who rent the one bedroom don’t want to share  the same bedroom.
 I told airbnb  I don’t want to do another listing because it means I  risk to have 2 different bookings from 2 different people who don’t know each other and I don’t want that. I want to book 2nd room only if  people know each other. 
Has anyone else had same issue? Is there any other way to add extra cost for letting a second bedroom? 

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[Huma0]

@Raymonde22 

No. As far as I know, you need to create two separate bookings and keep an eye on the calendars so the property doesn't get double booked.

If you use instant booking, that is more difficult, but what you could try is putting the option that gets the most bookings on IB and the other on request booking only, i.e. turn off IB. So, if you mostly get guests booking for just one bedroom, make that one the listing with IB. Hope that makes sense.