Being billed for breach of contract when I had a m

I app**** for a contract with Telkom. They came and installed the line and was off. After two days a message apearred that stated my data was low. When I called in to my shock I heard they installed a 4 meg capped 10 gig line. They rectified it and said it was there fault and that I am on a 4meg uncapped month to month contract. I could never reach 4meg ans the max was 2 so I called them again and the lady informed me that I am on paying for a 4 megd they can only give me 2 speed and that I need to downgrade to a 2 megeed because they can not increase my speed very rudely at that point I decided to change over to mweb that helped and increased my speed to a 4 line speed Now I get a bill from telat says I breached my contract with the but I had a month to month with them My brother inlaw app**** for a 2 meg unchapped month to month and when the line was installed they did the same to him After a day it displayed his data was diplenished and when he called in he was also hit with a 10 gig capped month to month witch he did not app**** for So this is what Telkom is doing to there customers to get them to pay for 24months and when they end it gets hit with a breach of contract