Beats speaker recall - No refund

Having been advised that the speaker was faulty/dangerous I followed the return procedure and waited. I was advised it would take three weeks but it has now been more like three months. My attempts to chase are as follows

1. Apple support requires the serial number before it will go beyond the opening screen. I of course don't have this as the speaker has been returned. Should have noted it of course but as it was typed onto the support web screen I didn't think I would need it.
2. My case number 626491720 is unrecognisable
3. The case number is not included against my Apple account so I can't access support by that route. This is despite the returns process using this account in the first place.
4. I can't even book a support call because I don't have the serial number and the required product ref is not on the drop down screen.
5. My product is not on any of the Apple screens so can't get in by that route either. I even had to add it on this site.

HELP