Cannot increase max_post_size or upload limits through WordPress

Hi, I need to upload a backup file through a WordPress plugin which requires 500 MB upload limits or max_post_size. I tried everything from my knowledge but nothing changed! My cPanel file upload limit is set to 1.5G but the WordPress shows 128M. 1. I tried max_post_size from cPanel > Select PHP Version > Switch to PHP Options. But the max_post_size set to 128M. Cannot increase more than the default. 2. Tried with .htaccess and php.ini file but nothing happens. 3. Tried from WHM > MultiPHP Ini Editor > Post Max Size set to 1024M but not reflecting on the WordPress upload limits. Please help me. How to increase the max_post_size and file upload limits of PHP settings? Thanks