Cancelling with penalties - disgraceful!! Steeling from customer!

I'm trying to cancel my parents mobile account with Telkom, as they don't get proper internet (wifi) signal now for months. They pay for a 20mbps signal but only get 2mbps. With other words, they get ****** out of a service they pay for but don't get. Now, they don't want it anymore and now they must pay penalties (which they actually can't afford - pensioners) because Telkom put them on a contract (without his consent) after he said to them that he wants to pay month to month basis. But did they listen? Oh hell no, that doesn't have ears to listen to customers request!! Cancel this contract WITHOUT penalties!!