I hope you didn’t pay a lot.
It has been said that the Costco aids are transferable. The normal way is for the owner to go with the person and transfer their ownership. You then need to be a Costco member to get support which will include reprogramming and basic supplies - not batteries. This runs for the life of the aids.
If you can get the person you bought them from to do this, you have a chance at getting Costco support. You’ll need some documentation for that from the person transferring the aids.