My elderly mother returned her broadband kit some months ago (and she has proof of postage).
She got multiple (worrying!) reminder emails about returning it.
She finally got an email stating it had been returned.
She's had more reminder emails since.
You've now sent her a £50 bill for not returning it!! She will not be paying it.
Ask her to select the 'message now' option on this link https://www.bt.com/help/contact-bt/account-and-billing/broadband to have a live chat with a billing guide, they'll get her sorted.
Hi @rwks and thanks for posting.
I'm sorry your mum has had a charge for the equipment after returning it. This should be automatically refunded but I can make sure everything is in order. Check your inbox for my message and drop me over the details. Or you can follow @Keith_Beddoe advice and contact the live chat guys.
Cheers
David