@rooman
Same thoughts as MB Themes here.... If my father wants to sell his car but doesn't know how to use the computer because he is already 80 years old and ask me to put it on the internet with his phone number because i don't want to answer all his potential buyers.
Anyway if you want to make the field readonly you can do it by adding in item-post.php
<script> $("#contactPhone").attr("readonly",true); </script>
So it looks like this copy / paste:
<div class="row phone">
<label for="phone"><?php _e('Phone Number', 'epsilon'); ?><?php if(strpos($required_fields, 'phone') !== false) { ?><span class="req">*</span><?php } ?></label>
<div class="input-box">
<?php if(method_exists('ItemForm', 'contact_phone_text')) { ?>
<?php ItemForm::contact_phone_text($prepare); ?>
<?php } else { ?>
<input type="tel" id="sPhone" name="sPhone" value="<?php echo $prepare['s_phone']; ?>" />
<?php } ?>
<script> $("#contactPhone").attr("readonly",true); </script>
</div>