Cancelled in May 2017 processed in September 2017

So we cancelled our subscription with you for our Adsl line in May 2017. You only confirmed cancellation in September 2017 and now you making us pay the outstanding debit up until September. Where is the 30 days cancellation clause been followed here on your side. Its absolutely rediculous and now you've handed is over for your *********** admin s****s. I have requested numerous times from Nudebt only the invoices we owe as it will be May month and we are prepared to pay it but why the hell should we pay all the other months when it was your own damn fault for not cancelling in time upon our request. Its unfair customer service and now that we want to pay rightfully what we owe this is what we get.