Returned old Router but BT saying they haven't received it

[tfarm]

I have returned my old router as requested but BT are saying they haven't received it and are threatening to charge me £50, who do I need to contact to resolve this? Thanks

[DanielS]

Hi @tfarm,

You will receive emails about returning the device until we have successfully logged and tracked your returned equipment against your account. There may be an overlap happening between receiving and updating your account. I am sorry that this has happened. I'll get this looked into for you. Reply back to my private message when you get a chance.

Thanks
DanielS