The new WC Insurance will most likely not have anything to do with this injury. The Insurance that was in effect at the time of your injury will own your claim until you close it. Whether the prior carrier will help you or not, it is their responsibility if you are still owed treatment.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.
I agree that the previous work comp carrier is the one on the hook for your continued medical unless you have aggravated the condition on your job and made it worse. In that case the old ins co and the new one will point fingers at each other. You will need an attorney if this is the situation
The insurer at the time of the accident is on the hook for your injury for life. However, in some cases, Employers are self-insured so the new insurer (who is actually a case manager) might take over those files. Your best bet is to contact your prior insurer. You probably need to hire a lawyer in Alabama to pursue payment for your surgery if the previous insurer is not cooperative.