Double debit order

I had an increase over December which I did not mind paying. This month a double wammy without any phone call to tell me. I phone them and they say it is because of my income bracket which I sorted out in October 2015. I want to know who gave them permission to take what they want out of my account and also I want to see the signature or listen to a voice recording. Excuse after excuse. I have had it. Now they will not refund all the money that was taken off my account and I have now cancelled the medical aid due to a bunch of ******* who.