I ordered a storage box containing 20 items. It was a special offer price; let's say it cost £20.
I also bought an additional 20 items costing £15 (no storage box.)
They also sell the same storage box containing 10 items for £15. I didn't order this.
They sent me the storage box with 10 items (not the 20 I ordered) plus the additional 20. I asked to be sent the missing 10. They said they can't do that but will refund me the £5 difference between the 10-item box and the 20-item box. That's not acceptable to me because the 10 missing items are worth at least £7.50, as 20 of them costs £15. I wouldn't have bought the 10-item box for £15 as I don't think it's good value.
AIBU to think they should refund me at least £7.50?
I suppose the alternative is to return the box with the 10 items for a full refund (not as described) and then re-order the box with 20 items, which is still on sale at that price but not likely to be so for much longer. It's the inconvenience, though. The original packaging was damaged (but the contents were intact) so I can't re-use it, so I'll have to find some other packaging. Also would they have to pay for the return?