JSFiddle - React, Tailwind, and code Playground

HTML

<select name="Solicitors" id="Solicitors" class="Solicitors">
<option value="0" selected="selected">--Select Solicitor--</option>
<option value="1" data-tel="020 8564 1245" data-email="[email protected]">Steven Petrie</option>
<option value="2" data-tel="020 8716 1249" data-email="[email protected]">Sue Wood</option>
</select>

<br>
<br>

<input type="text" name="phn" id="phn">
<br>
<br>
<input type="text" name="mal" id="mal">

JavaScript

$('#Solicitors').change(function() {
    var solicitor = $("#Solicitors option:selected");
    var solicitorID = solicitor.val()
    var solicitorPhoneNo = solicitor.data("tel");
    var solicitorEmail = solicitor.data("email");
		
    document.getElementById("phn").value = solicitor.data("tel");
    document.getElementById("mal").value = solicitor.data("email");
});