Hide the 'Cancel' button until the payment count reaches '12'.

wcs_remove_cancel_button_MIN.php

<?php

function wcs_remove_cancel_button_MIN ( $actions, $subscription ) {
    if ( $subscription->get_completed_payment_count() >= 12 ) {
        return $actions;
    }
    unset( $actions['cancel'] );
    return $actions;
}
add_filter( 'wcs_view_subscription_actions', 'wcs_remove_cancel_button_MIN', 100, 2 );