Deducting premiums when they feel like it, not when I authorised it!!!!!!!!

I tried to call Standard Bank Insurance because suddenly my insurance premiums are deducted on the 18th of the month and not on the end of the month as arranged. After holding on for more than a hour and being transferred to 5 different divisions each telling me they need to put me through to another division, I gave up. I'm not prepared to sit my whole day holding on for someone that can explain, why they are deducting premiums on dates that I didn't authorized. The way I'm feeling now is to cancel all policies with them. How helpful will they be when a claim needs to be done against one of these policies. Terrible service.