Dar- My experience is renaming them works. My baby Maggie was named HGT by the stupid breeder. I don't even know what they called for the first four years of her life her but after a few months she answered to Maggie. And sometimes Heidi but that is my fault they sound a lot alike. Heidi only answers to Heidi and princess.

My parents renamed their adult stray, Athena. She answers to it just fine. She was probably 2 when they got her 6 years ago so definitely had some name.

Obviously if you know what they were named it is easier but they eventually learn.