diff --git a/EGLDSender.py b/EGLDSender.py
index 6b63c86..fc1b1b7 100644
--- a/EGLDSender.py
+++ b/EGLDSender.py
@@ -43,13 +43,27 @@
 # Get the data message
 data = " ".join([str(item) for item in args.data])
 
+# ---------------------------------------------------------------- #
+#                         CONSTANTS
+# ---------------------------------------------------------------- #
+
+config_network = {
+    "mainnet": {"chainID": "1", "proxy": ""},
+    "devnet": {"chainID": "D", "proxy": "devnet-"},
+    "testnet": {"chainID": "T", "proxy": "testnet-"}
+}
+
+CHAIN = "mainnet"
+CHAIN_ID = config_network[CHAIN]["chainID"]
+PROXY = config_network[CHAIN]["proxy"]
+
 # ---------------------------------------------------------------- #
 #                   MAIN EGLD FUNCTION
 # ---------------------------------------------------------------- #
 def sendEGLD(owner, owner_on_network, receiver, amount, signer):
 
     payment = TokenPayment.egld_from_amount(amount)
-    config = DefaultTransactionBuildersConfiguration(chain_id="1")
+    config = DefaultTransactionBuildersConfiguration(chain_id=CHAIN_ID)
 
     builder = EGLDTransferBuilder(
         config=config,
@@ -79,7 +93,7 @@ def sendEGLD(owner, owner_on_network, receiver, amount, signer):
 pubkey = bytes.fromhex(pem.public_key.hex())
 owner = Address(pubkey, "erd")
 
-provider = ProxyNetworkProvider("https://gateway.multiversx.com")
+provider = ProxyNetworkProvider(f"https://{PROXY}gateway.multiversx.com")
 owner_on_network = provider.get_account(owner)
 
 # ---------------------------------------------------------------- #
diff --git a/ESDTSender.py b/ESDTSender.py
index de5338f..dc5c1ee 100644
--- a/ESDTSender.py
+++ b/ESDTSender.py
@@ -6,6 +6,8 @@
 from pathlib import Path
 
 import argparse
+import requests
+import sys
 
 import pandas as pd
 pd.options.mode.chained_assignment = None  # default='warn'
@@ -44,16 +46,33 @@
 # ---------------------------------------------------------------- #
 #                         CONSTANTS
 # ---------------------------------------------------------------- #
+
+config_network = {
+    "mainnet": {"chainID": "1", "proxy": ""},
+    "devnet": {"chainID": "D", "proxy": "devnet-"},
+    "testnet": {"chainID": "T", "proxy": "testnet-"}
+}
+
+CHAIN = "mainnet"
+CHAIN_ID = config_network[CHAIN]["chainID"]
+PROXY = config_network[CHAIN]["proxy"]
+
 TOKEN_DECIMALS = args.decimals  # default : 18
 TOKEN_ID = args.id
 
+try:
+    response = requests.get(f'https://{PROXY}api.multiversx.com/tokens?identifier={TOKEN_ID}')
+    response.raise_for_status()
+except requests.exceptions.HTTPError as e:
+    print("ERROR: Token does not exist")
+    sys.exit()
 
 # ---------------------------------------------------------------- #
 #                   MAIN ESDT FUNCTION
 # ---------------------------------------------------------------- #
 def sendESDT(owner, owner_on_network, receiver, amount, signer):
     payment = TokenPayment.fungible_from_amount(TOKEN_ID, amount, TOKEN_DECIMALS)
-    config = DefaultTransactionBuildersConfiguration(chain_id="1")
+    config = DefaultTransactionBuildersConfiguration(chain_id=CHAIN_ID)
 
     builder = ESDTTransferBuilder(
         config=config,
@@ -80,7 +99,7 @@ def sendESDT(owner, owner_on_network, receiver, amount, signer):
 pubkey = bytes.fromhex(pem.public_key.hex())
 owner = Address(pubkey, "erd")
 
-provider = ProxyNetworkProvider("https://gateway.multiversx.com")
+provider = ProxyNetworkProvider(f"https://{PROXY}gateway.multiversx.com")
 owner_on_network = provider.get_account(owner)
 
 # ---------------------------------------------------------------- #
diff --git a/README.md b/README.md
index 634ad9b..cc74bbc 100644
--- a/README.md
+++ b/README.md
@@ -19,15 +19,12 @@ All libraries versions are in the requirements file, and they can be installed w
 
 You need also need a [walletKey.pem](https://docs.multiversx.com/sdk-and-tools/sdk-py/deriving-the-wallet-pem-file/#__docusaurus/)
 
-## Devnet
+## Devnet & Tesnet
 
 In order to use the Devnet you need to: <br><br>
 Change this line: 
-```provider = ProxyNetworkProvider("https://gateway.multiversx.com")```
-and use this gateway: ```https://devnet-gateway.multiversx.com```
-
-Change this line: ```config = DefaultTransactionBuildersConfiguration(chain_id="1")```
-use ```chain_id="D"```
+```CHAIN = "mainnet"```
+and use this gateway: ```"devnet"``` or ```"testnet"```
 
 ## CLI
 
diff --git a/multipleESDTSender.py b/multipleESDTSender.py
index 3292020..d5f18bb 100644
--- a/multipleESDTSender.py
+++ b/multipleESDTSender.py
@@ -8,6 +8,8 @@
 
 import json
 import argparse
+import requests
+import sys
 
 import pandas as pd
 
@@ -50,9 +52,27 @@
 # ---------------------------------------------------------------- #
 #                         CONSTANTS
 # ---------------------------------------------------------------- #
+
+config_network = {
+    "mainnet": {"chainID": "1", "proxy": ""},
+    "devnet": {"chainID": "D", "proxy": "devnet-"},
+    "testnet": {"chainID": "T", "proxy": "testnet-"}
+}
+
+CHAIN = "mainnet"
+CHAIN_ID = config_network[CHAIN]["chainID"]
+PROXY = config_network[CHAIN]["proxy"]
+
 TOKEN_DECIMALS = []
 TOKEN_IDs = []
 for index, id in enumerate(args.ids):
+    try:
+        response = requests.get(f'https://{PROXY}api.multiversx.com/tokens?identifier={id}')
+        response.raise_for_status()
+    except requests.exceptions.HTTPError as e:
+        print(f"ERROR: Token {id} does not exist")
+        sys.exit()
+
     if index < len(args.decimals):
         TOKEN_DECIMALS.append(args.decimals[index])
     else:
@@ -69,7 +89,7 @@ def sendMultipleESDT(owner, owner_on_network, receiver, amounts, signer):
         payment = TokenPayment.fungible_from_amount(TOKEN_IDs[index], amount_to_send, TOKEN_DECIMALS[index])
         payments.append(payment)
 
-    config = DefaultTransactionBuildersConfiguration(chain_id="1")
+    config = DefaultTransactionBuildersConfiguration(chain_id=CHAIN_ID)
 
     builder = MultiESDTNFTTransferBuilder(
         config=config,
@@ -96,7 +116,7 @@ def sendMultipleESDT(owner, owner_on_network, receiver, amounts, signer):
 pubkey = bytes.fromhex(pem.public_key.hex())
 owner = Address(pubkey, "erd")
 
-provider = ProxyNetworkProvider("https://gateway.multiversx.com")
+provider = ProxyNetworkProvider(f"https://{PROXY}gateway.multiversx.com")
 owner_on_network = provider.get_account(owner)
 
 # ---------------------------------------------------------------- #
diff --git a/requirements.txt b/requirements.txt
index 4ea4ebc..5a8d257 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
 pandas==1.4.1
-multiversx-sdk-core===0.3.3
-multiversx-sdk-wallet===0.4.2
-multiversx-sdk-network-providers===0.6.7
+multiversx-sdk-core===0.4.1
+multiversx-sdk-wallet===0.6.2
+multiversx-sdk-network-providers===0.6.9
\ No newline at end of file