I have worked as a courier for 26 years.  This week, my company hired a third party courier company who will handle all courier deliveries.  I have been offered an office job in the lab, which has slightly less pay overall.  I don’t agree to these changes.  Do I have any recourse?  

If your job and responsibilities are going to be substantially different along with a pay cut, this is usually considered as the type of change that you may not have to accept.  You should tell the employer that you disagree with the changes and insist that your job and pay remain as before.  If, after 26 years on the job, they are not prepared to act reasonably with this request,  you could treat yourself as though you have been terminated, by leaving your job and suing for lost wages while you look for another job.