My wife had pre booked a seat, but on checking in found she had been moved to a B seat.

I asked customer services what was going on and got the following answer:

Dear Chris, it is clearly stated on the website that seat numbers are not guaranteed but the seat type is, final seat assignments remain a privilege of the cabin crew as also stated on the website, I am sorry but the payment for a pre-selected seat is non refundable, rgrds/Mijisa

Given that we already had purchased an undefined seat in economy class I have to wonder what we actually bought when we paid to pre reserve the seat.....