Charging over additional R2000 fo installment

I have had my vehicle financed with ABSA for a year and a half. Prior to taking delivery of my vehicle I had to supply proof of insurance. Which I did. This month ABSA has decided that because they have clients that cancel their insurance after taking the vehicle they decided to increase my instalment by over R2000 for insurance. I have contacted the departments and have proven once again that I have insurance. I have asked for someone to contact me with regards to this via email and via telephone but no one has the curtsey of returning my calls. This is shocking service. ABSA is quick to remove money out of your account and adjust your policy as they feel but wont even return your call or reverse your transaction when they have stuffed up. They treat you as if you are at fault and then must just accept what has happened as they are always right. Lets see if they will even contact me now. I wont hold my breathe as they may charge me for that too. SHOCKING.