Exploitation of people by big companies.

Guys I'm confused when you have a contract from Jan 1 to December 2. When you get to December 2 doesn't that mean our contract if finished if I choose not to renew. So why are we getting these companies saying we owe them money when we have made our last payment. I have never in my life signed a contract then in the end be told that I have to come back and cancel after my contract is up. This is very annoying and unfair because when you do try and cancel their contracts you get sent from pillar to post if they do happen to answer their phones. In the end this ends up dragging for years yet they have recorded calls to help resolve such issues. These companies are exploiting us on another level, imagine being told you have to pay for their mistakes and faults and there is nothing you can do except for that if you don't want your name to end up in ITC. In such cases who is meant to help us out. And by the looks of things these cases are just getting worse by the day. Can someone please help us we can't be getting exploited like this with laws we know nothing about. Shame on you Telkom and MTN your services suck. I'm disgusted issues that have been dragging since 2017 and still not resolved.