Add a notice before or after the list of subscriptions in the My Account 'Subscriptions' tab.

notice__before_after_subscriptions_list.php

<?php

/*
 *
 * Before subscriptions list in the My Account 'Subscriptions' tab.
 *
 */
function notice__before_subscriptions_list( $has_methods ) { 
    wc_print_notice( __( 'These are your current subscriptions...', 'woocommerce' ), 'notice' );
};
add_action( 'woocommerce_account_subscriptions_endpoint', 'notice__before_subscriptions_list', 9, 1 );

/*
 *
 * After subscriptions list in the My Account 'Subscriptions' tab.
 *
 */
function notice__after_subscriptions_list( $has_methods ) { 
    wc_print_notice( __( 'These are your current subscriptions...', 'woocommerce' ), 'notice' );
};
add_action( 'woocommerce_account_subscriptions_endpoint', 'notice__after_subscriptions_list', 11, 1 );