try this in web.config where the services are configured.
<system.diagnostics>
<sources>
<source name="System.ServiceModel" switchValue="Verbose,ActivityTracing" propagateActivity="true">
<listeners>
<add type="System.Diagnostics.DefaultTraceListener" name="Default">
<filter type=""/>
</add>
<add name="ServiceModelTraceListener">
<filter type=""/>
</add>
</listeners>
</source>
</sources>
<sharedListeners>
<add initializeData="C:\\Users\\santhosh.kumar\\Desktop\\LS Evaluations\\Logs" type="System.Diagnostics.XmlWriterTraceListener, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" name="ServiceModelTraceListener" traceOutputOptions="Timestamp">
<filter type=""/>
</add>
</sharedListeners>
</system.diagnostics>
and in your service behaviors add the below line.
<servicedebug includeexceptiondetailinfaults="true">
Sample:
<behavior name="UtilityServiceBehavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
</behavior>