Horrible service

I took a contract with Mondo, Telkom is the network and I took a router... Number linked to the router ***

I finished paying for that contract last year already and I've been calling them asking them nicely to close the contract for me but they don't want to assist me, now I'm sent a statement stating that I'm owing me because I reversed and stopped their debit order on my bank and I will not pay what you say I owe because I've been calling, speaking to different agents that I want the contract closed and I won't be renewing because I have financial issues and nothing has been done I'm soooo mad