Make sure the Contact Form plugin is installed.
<form id="contactForm" action="../../local/contact/index.php">
<div class="row">
<div class="col-lg-6 col-md-6">
<div class="form-group">
<input type="text" name="name" id="name" class="form-control" placeholder="Name">
</div>
</div>
<div class="col-lg-6 col-md-6">
<div class="form-group">
<input type="email" name="email" id="email" class="form-control" placeholder="Email">
</div>
</div>
<div class="col-lg-6 col-md-6">
<div class="form-group">
<input type="text" name="phone_number" id="phone_number" required class="form-control" placeholder="Phone No">
</div>
</div>
<div class="col-lg-6 col-md-6">
<div class="form-group">
<input type="text" name="msg_subject" id="msg_subject" class="form-control" required placeholder="Subject">
</div>
</div>
<div class="col-lg-12">
<div class="form-group">
<textarea name="message" class="form-control" id="message" cols="30" rows="6" required></textarea>
</div>
</div>
<div class="col-12">
<div class="form-check">
<div class="form-group">
<div class="form-check">
<input name="gridCheck"
value="I agree to the terms and privacy policy."
class="form-check-input"
type="checkbox"
id="gridCheck"
required >
<label class="form-check-label" for="gridCheck">
I agree to the <a href="#">Terms & conditions</a>
</label>
</div>
</div>
</div>
</div>
<input type="hidden" id="sesskey" name="sesskey" value="">
<script>document.getElementById('sesskey').value = M.cfg.sesskey;</script>
<div class="col-lg-12 col-md-12 text-center">
<button type="submit" class="default-btn">
Send Message
</button>
</div>
</div>
</form>