Simply Be have lost my return

[QuestionableMouse]

I sent two pairs of trousers back on Monday and they're saying they still haven't received them even though I used the courier they provided. He asked me to sign the tablet thing but didn't give me any paperwork so I have no proof. Have a feeling its £40 down the drain which I can ill afford.

(They were sent back because one was about two sizes smaller than labelled and the other were miles too long despite being sold as a short)

I've been in touch with them but they're asking for proof and don't seem to believe that I wasn't given any. (I asked and was told my signature was enough.)

AIBU to be pissed off and wondering what to do next?

That's quite a quick turn around for returns - mine takes just over a week.
Which courier service does SimplyBe use?

Can you remember the time he collected your parcel? - if you signed on his hand device it should be recorded on there, and the data sent to wherever it's stored.
Do you know the courier's name?
Have you the couriers phone number - to help identify him.
Can you give a description of him?

My courier (Hermes for jdwilliams) has two physical labels for any returns of mine - one goes on the bag and one on to a photocopy of the original invoice of the goods I'm returning. These labels have matching identical numbers on them, so I can prove the courier collected them.

Last time I returned stuff to Simply Be it took about two or three weeks to process it.

They are very slow.

I've given them as much information as I can so hopefully it'll work out. Just annoying because now I'm worrying I'm not going to get my money back and not have the trousers either.