Bad Service let to i have pay for it every month..... I want My debit Order Cancel like the first time i ask 3 months back.!!!!

I called 3 months back to ask them to cancel my debit order that i will pay it cash due to personal Reasons. But no 3 months im paying more for my phone due to penalties fee of debit Order... I want my debit Order to be stopped.. The lady i spoke to told me if pay it on 25 the of each month there will be no penalties fee but f*ck knows im paying on 25 the and still pay f*ck penalties fee.......!!!