failure to provide service - adsl

i've taken adsl 24 month contract with telkom which i was paying 209 and contract was supposed to end October or November 23. From March this year they start billing me R375 without any explanation. i phoned them which they fixed for March debit order. fo i experienced some connectivity issues my line didn't work yet they still bill me 375 for April again. the technician came and they told me they would fix my line because they have discontinued adsl i must upgrade to fibre. i phoned telkom that i have 24 month contract and not interested in fibre because now i was supposed to pay R549. i stayed without internet the whole of May and month end they still debit my acccount R375 of which i reversed because i'm not receiving any service yet im expected to pay an amount of which is not my monthly debit order of 209. telkom have ruined my name @credit burea yet they are the one who failed to uphold their 24month contract. how can one be expected to pay while they are not receiving any services.