@cfm168 Out of the box, the Checkout page in WooCommerce includes a phone field for both the billing and shipping addresses. If it isn’t showing on your site, I’d recommend reviewing the settings for the phone filed under Appearance > Customise > WooCommerce > Checkout.
If the setting there isn’t Hidden, but it still doesn’t show, then it’s possible that other software on your site might be hiding the option. In this case, I’d recommend running a full conflict test.
You’ll want to temporarily switch your theme to Storefront. Then, disable all plugins on the site except for WooCommerce, and test for the issue.
If the issue is gone, you’ll then have to re-enable features one by one, while testing for the issue; until you find out which one is causing this behavior.
We recommend that these steps are taken on a staging site, which is a clone of your live site that you can modify without risking making any permanent damage to your live site. You can create it using a plugin like WP-Staging: https://www.ads-software.com/plugins/wp-staging/
This plugin lets you copy and redeploy a WordPress site with minimal work.