CELL C Robbing my of my Money without providing any service

I've am fedup with Cell C! I've cancelled my Contract with them in December 2018 and the still have the audicity to collect money from me every month!!

They sold a LTE Router to me after my previous contract expired, knowing very well it will not work in the area where I am residing! The device was returned to them the beginning of December 2018, the sim card is not in use for 7 months!!!!

I've emailed them, I was on the phone with their useless customer service agents for hours, they keep on passing the bucket! I've waisted a lot of time and money and still they take money from my bank account EVERY MONTH!!! Don't know for what........NO DEVICE NO SIM CARD?