Please edit your code as below:
<address class="address_phone">
<span class="icon icon-phone"></span>
<div class="contact_title"><?php echo esc_html__('Phone:', 'yogastudio') ?></div>
<span class="contact_item phone">
<?php if (!empty($phone)) { echo '<a href="https://wordpress.stackexchange.com/questions/346269/tel:".$phone.'">'.esc_html($phone).'</a>';} ?>
</span>
</address></div><div class="column-1_3">
<address class="address_email">
<span class="icon icon-mail"></span>
<div class="contact_title"><?php echo esc_html__('Email:', 'yogastudio') ?></div>
<span class="contact_item mail"><?php if (!empty($email)) { echo '<a href="https://wordpress.stackexchange.com/questions/346269/mailto:".$email.'">'.esc_html($email).'</a>';}?></span>
</address></div>