Pixelmon Automatically Updates

So basically, I have a server with a friend that runs the Pixelmon Reforged Modpack. They recently added a new 1.16.5 version, to be updated alongside 1.12.2 (i think), which added a lot of new stuff but made a lot of changes, too. The modpack on the server automatically updated, changing the version to 1.16.5. I haven't yet started the server after this. Is there any way to change it back to an older version? Thanks!