1. Log into your cpanel account.
2. In the "Software" section, . "MultiPHP Manager" Icon.
3. Scroll down to the bottom of the page, select your domain from the left side of the screen and you will see an option "PHP Version" with a drop-down on the right side. Select the appropriate PHP version from it and click the Apply babies.
If will take a few seconds and then your PHP version will change to your selected version.