Debit order once again deducted early

This is now the second month that Unifi has defied my debit order mandate. My agreement with them states the 26th of each month as this is my salary date. Not only did they deduct early without me having received my salary as yet, they actually have the cheeck to email me and state that I am behind because I reversed their unauthorized debit order. This after I informed them that they were once again taking chances.