If your browser is bundled with the Skype plugin, it will automatically wrap the phone number with Skype format. This can be avoided by adding a invisible text anywhere in the phone number.

<!-- Orginal -->
<div>852 12345678</div>
<!-- Prevent the Skype plugin to work -->
<div>852 1234<span style="display:none;">_</span>5678</div>

Done =)

Reference: 1066internet – Prevent Skype from converting a phone number