Router not collected

I received an email stating they will collect the router by sending a courier to me, after I cancelled with them. Till today, no courier has even contacted me. Vox now keeps bombarding and threatening me to hand me over if I dont pay R1999-00. I have rep**** to all their mails to tell them to send the courier, i have someone at home to hand it over. I have previously had issues with them and has since cancelled with them for poor service. I do have an email trail and will definitly take this further if they dont contact me via email and resolve this. How do you get these people off your back? I dont encourage people to make use of their service, spare yourself the anger and headaches.