Several web hosts offer the ability to change your version of PHP through the cpanel / hosting panel area. Try searching their support area to see if that is available.
If it isn't, then here is a message that you can share with your web host in a support ticket. Be sure to change example.com to your actual website URL.
Hello! I’m using an ecommerce plugin called Event Espresso on my WordPress site: example.com My WordPress site is using an older version of PHP. Could you please help me switch my site to a current version of PHP? Thank you!
Our recommended WordPress hosts all support a current version of PHP: https://eventespresso.com/requirements/