Unauthorized billing on a cancelled contract

I took on a month to month data contract a year ago @ R460 PM, decided to cancel it as i opted for fibre as their connectivity wasn’t great i made sure that everything is cancelled and the router is returned on the last day of the month however they still debited me me for a full subscription the following month i kept my cool and escalated a case and it got worse the second month they decided to debit my account again an amount of R2500 unauthorized when I called in they told me i was charged for a router and i should go into the store for an explanation, when i hot to the store they called the repair center and they stated that the router was damaged utter fabrication as the router was in good condition as i live alone with no dependents or pets I asked for proof of such which was never supp**** i was forced to take they word for it, my question was when booking in a device doesn’t it go under assessment first and make notes in front of the customer so they are aware of any issues i know other network providers do to avoid any further issues they said no and I requested for pictures of the damage and i was denied luckily i took my own picture before handing it in and i will take this matter further and open a case against them as this is pure bullying and unprofessional working ethic, how many innocent people are you doing this to especially people who don’t know their rights well it stops with me i will fight this company for all it’s worth as this behavior is disgusting no wonder their market share dropped.