Unauthorised Funeral cover amount increases

FNB decided to increase my funeral plan, because I did not reply NO for the cover increase amount. When I called in they said I should have reply No to the message they have send. I have no obligation to reply to any message that is costing me money. I took a certain amount for funeral plan because that's what I needed. FNB have no right to decide on my behalf how much I need for a funeral plan. I requested for the premium amount to be reversed to what I agreed on. They did reverse the increased premium, but never refunded me for increase amount that was deducted without my consent. Who is FNB to decide to increase the insured amount, which the premium obviously also when up.