unauthorised debit order for the 2nd time in a few days

this has been the second debit order from my account,on the 26th sep miway deducted my premium from account,on th e1st octer they deducted another premuim when i called them they told me that the system automatically raised a debit order on my account.yesterday 11.10.2018 they debited another premuim from my account when i called in and spoke to the consultant she then told me if i make any changes to my policy before the new debit order date then the system automatically raise a debit order how is that possible when i payed for the month and if i make any changes to my policy it should only come to effect in the new month cause ive already paid for the month something is not right here and its costing me money and bank fees.im happy with the service i receive from them its just that they just cant debit my account with out me knowing about it.