If you have been attempting to handle your claim by yourself and you now need surgery it is not adviseable you continue to represent yourself. You should consult with three to five personal injury attorneys. Ask them how they would handle the fact that you need surgery and the insurance company will not pay for it. Make sure you are comfortable with their responses.
As far as I am concerned you should cease all communications with the insurance company until later. The at-fault insurance will not pay for your claim as you go, the only reason they are speak with you is so they can “value” or as they call it “set their reserves”. This does not help you at all and if you misstate some detail on your telephone conversation with them (that is recorded) it could actually hurt your claim.
You will likely need to file a lawsuit moving forward, this may have been avoided with hiring an attorney earlier in the claim it just depends upon the circumstances of the crash and the extent of pre-existing injuries you suffered prior to this wreck.