Booking.com complaint: Not getting the accommodation I had booked

I had booked an apartment through booking.com in Auckland called “apartment with a brilliant view” for 2 nights in Auckland 27,28 January, we booked this as it had 2 bedrooms, 2 bathrooms , a spacious living area,kitchen and balcony and we wanted somewhere spacious, When myself and my friend arrived at the address (17 Wakefield Street) we couldn’t get in as the doors were locked , we eventually were let in by a building manager who knew nothing about our booking and we didn’t have any key code to get into an apartment and we didn’t know which apartment was the one we had booked. There was also other people there in the same situation, after a lot of mucking around and many phone calls to booking,com which cost me approximately $60 in phone calls booking.com eventually found another hotel (Mercure Auckland Queen Street) for us to stay in, we hadn’t paid for the original hotel as we assumed we were paying on check in. Booking.com told me on the phone to get an invoice for the Mercure Hotel and as long as it didn’t cost more than $40 more than the original apartment that they would reimburse me for the whole inconvenience. So I sent them the invoice and they have refused to pay and said they had never said that they would even though I had the name of the person who told me this,and as I had my phone on speaker phone at the time 2 people with me heard her tell me this. After many emails to them they have stopped replying and have deleted all my messages so I have no way of contacting them now.
My main issue is that the Mercure Hotel was a tiny studio room with one bed, no kitchen, no living area, no balcony so was not comparable to what we had booked. Can you help with this situation to get this money back as promised please?
Confirmation number 2997204151. Confirmation number 3643523934
Mackenzie Kerslake