erasing the hard-drive Macbook pro

I have a 2013 macbook pro running Catalina version 10.15.4. In order to trade it in, I'm trying to erase the hard drive. In disk utility, the Container Disk, Macinitosh HD and Macintosh HD - Data selections have the erase icon greyed out. The only option that allows the process to continue is to select Appple SSD SM0256F Media. When that is selected, and the erase option, both the APFS and Mac OS Extended formats result in the error: Couldn't open device.: (-699877) How can I erase the SSD hardrive?