It is very common for health providers in wa to have a different time of service rate than if billed later. You may not have signed anything but by billing your insurance, likely signing something to okay that, your chiropractor has a contract with them for the rates they can bill and get paid for. If your insurance doesn’t end up paying it, because of your agreement with your health insurance, you are now liable for that payment. As to the things you were charged for, did you ask the chiro? Something as simple as applying heat can be billed as extra. The chiro has notes on what was performed and should be able explain the extra charges, but it would be good to ask for the explanation of what was billed and why.

Everyone is a bad driver from another drivers perspective. No one is going to cater to your sense of safety on the road. Half those people probably don’t have insurance either so you better make sure you see them anyway.