Unexpected charges by the their guests house( Mphohali Guest House Lesotho)

I made a booking for 12 guests through them for 2 nights 4 rooms 3 guests per room sharing. The bookings was confirmed as per reference no: *** PIN 7373 AND *** PIN 1173. every was okay up until the second night the the guest house when I wanted to pay for our stay.to my suprised the Guest House told me that I need to pay extra for 4 people for 2 nights stay because according to them (The Guest House) they don't accommodate 3 people per room of which it didn't make sense cause we had 4 rooms with 3 people sharing.

I took it up with the Booking..com hoping that I will get help but it's been 2 weeks now without any help. The last communication with booking.com they requested my bank statement as a proof of which I did send to them. Upon the follow-up I was then told been told that they need a an invoice from the Guest house of which I told them that the guest house didn't have a proper invoice but they gave me a stamped written that also submitted to them.

I have a couple of bookings lines up with them till the end of the year of which I am now thinking twice for using them