Increase of 50% on vehicle’s monthly premium WITHOUT PERMISSION

My policy’s monthly fee was increased by 25% in Sept 2018. One of my vehicles premiums alone was increased by just over 50%, where there were NO CLAIMS and NO CHANGES whatsoever. I have contacted the company many times and asked them to advise why the policy was increased with this massive amount, especially since I never received any communication to inform me that there will be changes. I do not view it as ethical or honest to increase fees by such huge amounts without permission from the client. I expect a full refund of the difference that was deducted monthly from my account since Aug 2018.