Unauthorized debit order change.

Budget insurance has started debiting my account a whole week before the date that I signed for. The reason I chose that date is because that is when I get paid. They are now trying to debit my account on the 19th of every month which means I have a bounced debit order every month that I have to pay penalty fees for. Will they reimburse me for these penalty fees? Bounced debit orders stay on your credit record for a long time after the fact so they are also affecting my ability to get finance.

I cannot understand why they think this is ok?