diff --git a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountChargeHandler.java b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountChargeHandler.java
index 0c12fe6..89d93a4 100644
--- a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountChargeHandler.java
+++ b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountChargeHandler.java
@@ -159,7 +159,7 @@ public boolean handle(MessageContext context) throws Exception {
             }
 
             sendingAddress = PaymentUtil.decodeSendingAddressIfMasked(executor, context, sendingAddress);
-            JSONObject objAmountTransaction = jsonBody.getJSONObject("amountTransaction");
+            JSONObject objAmountTransaction = jsonBody.getJSONObject(AttributeConstants.AMOUNT_TRANSACTION);
             if (!objAmountTransaction.isNull(AttributeConstants.CLIENT_CORRELATOR)) {
                 clientCorrelator = nullOrTrimmed(objAmountTransaction.get(AttributeConstants.CLIENT_CORRELATOR).toString());
             }
@@ -183,9 +183,11 @@ public boolean handle(MessageContext context) throws Exception {
                 clientCorrelator = clientCorrelator + ":" + hubGatewayId + ":" + appId;
             }
 
-            if (objAmountTransaction.getJSONObject("paymentAmount").has("chargingMetaData")) {
+            JSONObject paymentAmount = objAmountTransaction.getJSONObject(AttributeConstants.PAYMENT_AMOUNT);
+            if (paymentAmount.has(AttributeConstants.CHARGING_META_DATA) &&
+                    !paymentAmount.isNull(AttributeConstants.CHARGING_META_DATA)) {
 
-                JSONObject chargingMeta = objAmountTransaction.getJSONObject("paymentAmount").getJSONObject("chargingMetaData");
+                JSONObject chargingMeta = paymentAmount.getJSONObject(AttributeConstants.CHARGING_META_DATA);
 
                 boolean isAggregator = PaymentUtil.isAggregator(context);
 
diff --git a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountRefundHandler.java b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountRefundHandler.java
index f7ae3cd..94eff5a 100644
--- a/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountRefundHandler.java
+++ b/mediation-old/src/main/java/com/wso2telco/dep/mediator/impl/payment/AmountRefundHandler.java
@@ -29,14 +29,11 @@
 import com.wso2telco.dep.mediator.internal.ApiUtils;
 import com.wso2telco.dep.mediator.internal.Type;
 import com.wso2telco.dep.mediator.internal.UID;
-import com.wso2telco.dep.mediator.mediationrule.OriginatingCountryCalculatorIDD;
 import com.wso2telco.dep.mediator.service.PaymentService;
 import com.wso2telco.dep.mediator.util.*;
 import com.wso2telco.dep.oneapivalidation.exceptions.CustomException;
 import com.wso2telco.dep.oneapivalidation.service.IServiceValidate;
 import com.wso2telco.dep.oneapivalidation.service.impl.payment.ValidateRefund;
-import com.wso2telco.dep.subscriptionvalidator.util.ValidatorUtils;
-import com.wso2telco.dep.user.masking.configuration.UserMaskingConfiguration;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.http.HttpStatus;
@@ -45,7 +42,6 @@
 import org.apache.synapse.core.axis2.Axis2MessageContext;
 import org.json.JSONException;
 import org.json.JSONObject;
-import org.wso2.carbon.utils.CarbonUtils;
 
 import java.io.File;
 import java.util.HashMap;
@@ -194,11 +190,12 @@ public boolean handle(MessageContext context) throws Exception {
                 clientCorrelator = clientCorrelator + ":" + hubGatewayId + ":" + appId;
             }
 
-            JSONObject paymentAmount = objAmountTransaction.getJSONObject("paymentAmount");
+            JSONObject paymentAmount = objAmountTransaction.getJSONObject(AttributeConstants.PAYMENT_AMOUNT);
 
-            if (paymentAmount.has("chargingMetaData")) {
+            if (paymentAmount.has(AttributeConstants.CHARGING_META_DATA) &&
+                    !paymentAmount.isNull(AttributeConstants.CHARGING_META_DATA)) {
 
-                JSONObject chargingMetaData = paymentAmount.getJSONObject("chargingMetaData");
+                JSONObject chargingMetaData = paymentAmount.getJSONObject(AttributeConstants.CHARGING_META_DATA);
                 boolean isAggregator = PaymentUtil.isAggregator(context);
 
                 if (isAggregator && !chargingMetaData.isNull("onBehalfOf")) {
diff --git a/mediation-old/src/main/java/com/wso2telco/dep/mediator/util/AttributeConstants.java b/mediation-old/src/main/java/com/wso2telco/dep/mediator/util/AttributeConstants.java
index f1d0f6e..1e8b2a1 100644
--- a/mediation-old/src/main/java/com/wso2telco/dep/mediator/util/AttributeConstants.java
+++ b/mediation-old/src/main/java/com/wso2telco/dep/mediator/util/AttributeConstants.java
@@ -22,5 +22,7 @@ public class AttributeConstants {
     public static final String AMOUNT_TRANSACTION = "amountTransaction";
     public static final String CLIENT_CORRELATOR = "clientCorrelator";
     public static final String PURCHASE_CATEGORY_CODE = "purchaseCategoryCode";
+    public static final String CHARGING_META_DATA = "chargingMetaData";
+    public static final String PAYMENT_AMOUNT = "paymentAmount";
 
 }