Have Virgin received my prepaid return?

I've cancelled my Virgin account and was told I needed to return my kit by 9 Oct using the prepaid packaging. It took over 2 weeks for them to send me the packaging, which I then sent immediately once it arrived. They said it takes 10 days to process a return, but it's been over 2 weeks now since I returned the kit, but still haven't had any confirmation on where it is.

I've just received an email saying I will be charged £65 for not sending it, even though I know full well that I sent the kit back on Fri 24 Oct.

Annoyingly, the tracking information isn't coming up on the receipt I was given (just keeps saying parcel collected), and have tried so many times contacting Yodel/inpost to see if they can give me any updates on if the parcel was returned, but they're being super unhelpful too. 

I just want an update on whether you have my parcel or not. I will not be paying the late charges as I sent it well within the allotted time.