Contact Form 7 plugin, wordpress

Question

Form is working fine, all fields showing up. Although every dropdown select menu is showing an additional dropdown menu below itself.

The additional one below doesn't have border or css style, and due to my lack of experience in css I'm not sure why this is happening. The code looks fine, I've even copied examples from tutorials and it's still occurring to my dropdown select menus.

How do I stop this additional dropdown menu from appearing?

Form code:

<div class="form-row">
<div class="column-full">[response]</div>
<div class="column-full"><p class="heading">Your Details</p></div>
<div class="column-half">First Name [text* first-name]</div>
<div class="column-half">Last Name [text* last-name]</div>
<div class="column-half">Job Title [text* job-title]</div>
<div class="column-half">Email [email* your-email]</div>
<div class="column-half">Contact Ph [tel* contact-ph]</div>
<div class="column-half">How did you hear about us? [select* how-did-you-hear-about-us include_blank "Google" "Facebook" "Other social media" "Word of mouth" "Face to face sales" "A friend" "Other"]</div>
</div>

Answer 1

Sorry, have been away from the computer last couple days. So I found this code to fix the problem, although I have no idea what it's actually doing. Or if affects other things. I haven't noticed any other changes as yet, but it's removed the bit under the dropdown menu, so I'm happy about that:

 .sbHolder { 
 border-bottom: none !important; 
 } 

 .sbSelector { 
 display: none !important; 
 }