I've got the same issue mate, it quite clearly states on nokia website: SIM slot 1 nano-SIM slot + 1 nano-SIM or 1 MicroSD card slot.
And i definitely have the wrong tray. I used the online chat but that wasn't much of a help as someone kept suggesting i'm trying to put a sim card on top of a sd-card, blah blah blah
I read there was a similar issue with nokia 6 when in Fin;and and Russia people were getting the wrong tray.
I also have the guide that comes with the phone that clearly shows a hybrid tray and shows a way how to place 2 sim cards.
It doesn't even mention there could be a single-sim variant.
Also, on the back cover of my phone it says its a TA-1012 model, if you google that then you'll find quite many sources saying that TA-1012 is the dual sim variant
I got mine from Carphone Warehouse too, spoke to them and I got pretty much the same response
Nokia customer care just confirmed that my phone is a single sim version, based on the IMEI of my phone.
Yeah, I'll be returning mine too.