Please use WP Hooks, not brute force the PHP output buffer

Using output buffer to inject code is a horrible way to show the contact bar and will conflict with many plugins.

There is a reason WordPress hooks exist. It’s so you can customise the site in a way that plays nice with other plugins and themes.

Please consider using the wp_footer hook and CSS position:fixed to achieve the contact bar. You can use the WordPress admin bar as an example of how to do this.