Keep your equipment, it is not dead as a dodo

I had a Dodo contract for 2 years which expired, and have been on month to month because of NDN coming. Telstra called and offered to take care of everything NBN so I did it because ADSL is coming to a forced end.
I called Dodo to cancel and they want the modem back plus all the cables etc, everything that came in the box or I will be charged $109. Luckily I have everything. I had left everything in the box. They also wont cancel until it is returned