Economy Car Rentals review: Overcharged

I rented a car online through Economy Car Rentals. I was charged 127.40NZD immediately on booking. The voucher said I had 217 remaining to pay. I called ahead to see if I could get the car a bit earlier and was told that the insurance excess is 4,000 and I could purchase additional cover. I decided to get the excess waiver and ended up paying 388NZD for the four day rental. I have used this company before and was not charged anything prior to pick up so wondering why I was charged and why is this charge not included in the overall rental or deducted a s deposit? I have paid 200 deposit to the rental company before, but this time no deposit was charged and the 127 has not been refunded. The rental company was not helpful, telling me I had to talk to ECR, but they dont have a local branch in Wellington, no phone number and only a webform to fill out. I have a customer account but there are no contact numbers in that either. Seems like they dont want to talk to you, dont reply to emails and the receipt for the down payment does not specify what this charge is for. I did some digging online and they are a subsidiary company of AvisBudget, so the sales reps saying they cannot see anything online might be true or it might be they know its a scam and getting away with it. I will not rent through this company again and wish to warn others be careful if you are dealing with this company. They will happily sell you more products and as I have since learned the sales reps are getting commissions- incentives to agressively market extra products- buyer beware