BFTrick

<?php
// Filter the checkout fields
add_filter( 'woocommerce_checkout_fields', 'patricks_woocommerce_checkout_fields' );

// Remove the billing phone - $fields is passed via the filter
function patricks_woocommerce_checkout_fields( $fields ) {
    // remove the phone field
    unset($fields['billing']['billing_phone']);

    // make the billing email field fill up the entire space