I've seen this is a common issue. I called to cancel my virgin media broadband account on 23rd Feb as i was moving out of my flat and in with my partner who also has a virgin account. After an hour on the phone and being told there was no cancellation fee- I have been charged £18 disconnection fee. Then began the messages telling me I would receive a bag in the post to return the router, followed by messages saying I must return it within 9 days or get a £40 fine.
I have called twice to request new packaging to be sent out to return the router and told to wait 10 working days. I have also requested a new bag to be sent online. I have found all communications with virgin to be extremely stressful and have even had staff hang up on me.