'POST' \  'http://yourdomain.com/api/rest/contact/get' \
{
 "type":"MOBILE",
 "value":"48505606707"
}
JS 
<soapenv:Envelope
    xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
    xmlns:ecm="http://yourdomain.com/developer/ecmapi">
    <soapenv:Header/>
    <soapenv:Body>
        <ecm:contactGet>
            <identifier>
                <type>MOBILE</type>
                <value>48505606707</value>
            </identifier>
        </ecm:contactGet>
    </soapenv:Body>
</soapenv:Envelope>
JS

Response

Description

200From this request, you should receive a 200 response, with information about the contact. This includes information like their contactID.
400If the profile does not exist you will receive a 400 response. You can also double-check the number used in the call if you believe there is an existing user profile.