Keys and remote security devices are the responsibility of the owner to keep and maintain. It should have been given to you in working order. However batteries in such devices don’t last forever, and could result in a loss of code.
In my complex there is an automatic gate and the owners have from time to time run into problems with their remote devices. I have obtained replacement devices for owners, at their expense, when the originals were lost or damaged. Our owners are fortunate in that I am able to program these devices and do so without charge.
In essence your EC are correct in passing on the cost of programming your remote. In hindsight you should have sought recompense from the previous owner for the cost of fixing the inoperative remote.