diff --git a/pyproject.toml b/pyproject.toml
index ff08145..a58ba26 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=61.0"]
+requires = ["setuptools>=61.0,<70.0"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -17,8 +17,8 @@ classifiers = [
     "Operating System :: OS Independent",
 ]
 dependencies = [
-    "requests>=2.25.1",
-    "pydantic>=2.0.0"
+    "requests>=2.25.1,<3.0.0",
+    "pydantic>=2.0.0,<3.0.0"
 ]
 
 [project.urls]
diff --git a/src/paysgator/__init__.py b/src/paysgator/__init__.py
index d0cf227..a781604 100644
--- a/src/paysgator/__init__.py
+++ b/src/paysgator/__init__.py
@@ -1,3 +1,5 @@
+"""Paysgator SDK - A client library for the Paysgator API."""
+
 from .client import PaysgatorClient
 from .exceptions import PaysgatorError, AuthenticationError, APIError
 
diff --git a/src/paysgator/client.py b/src/paysgator/client.py
index a067367..5b0fb0f 100644
--- a/src/paysgator/client.py
+++ b/src/paysgator/client.py
@@ -50,10 +50,11 @@ def get_balance(self) -> WalletBalanceResponse:
         return WalletBalanceResponse(**response_data)
 
 class PaysgatorClient:
-    BASE_URL = "https://paysgator.com/api/v1"
+    DEFAULT_BASE_URL = "https://paysgator.com/api/v1"
 
     def __init__(self, api_key: str):
         self.api_key = api_key
+        self._base_url = self.DEFAULT_BASE_URL
         self.session = requests.Session()
         self.session.headers.update({
             "X-Api-Key": self.api_key,
@@ -66,13 +67,15 @@ def __init__(self, api_key: str):
         self.wallet = Wallet(self)
 
     def set_base_url(self, url: str):
-        self.BASE_URL = url
+        self._base_url = url
 
     def request(self, method: str, endpoint: str, data: Optional[dict] = None) -> dict:
-        url = f"{self.BASE_URL}{endpoint}"
+        url = f"{self._base_url}{endpoint}"
         response = self.session.request(method, url, json=data)
         
-        if response.status_code >= 400:
-             raise APIError(response.status_code, response.text)
+        if response.status_code == 401 or response.status_code == 403:
+            raise AuthenticationError(response.status_code, response.text)
+        elif response.status_code >= 400:
+            raise APIError(response.status_code, response.text)
         
         return response.json()
diff --git a/src/paysgator/exceptions.py b/src/paysgator/exceptions.py
index 3067741..5c0b53d 100644
--- a/src/paysgator/exceptions.py
+++ b/src/paysgator/exceptions.py
@@ -8,7 +8,8 @@ class AuthenticationError(PaysgatorError):
 
 class APIError(PaysgatorError):
     """Raised when the API returns an error"""
-    def __init__(self, status_code: int, message: str):
+    def __init__(self, status_code: int, message: str, response_data: dict = None):
         self.status_code = status_code
         self.message = message
+        self.response_data = response_data
         super().__init__(f"API Error {status_code}: {message}")
diff --git a/src/paysgator/models.py b/src/paysgator/models.py
index 8863e2d..00a1e4d 100644
--- a/src/paysgator/models.py
+++ b/src/paysgator/models.py
@@ -10,7 +10,7 @@ class PaymentCreateRequest(BaseModel):
     amount: float
     currency: str
     external_transaction_id: Optional[str] = Field(None, alias="externalTransactionId")
-    payment_methods: Optional[List[str]] = Field(None, alias="payment_methods")
+    payment_methods: Optional[List[str]] = Field(None, alias="paymentMethods")
     fields: Optional[List[str]] = None
     return_url: Optional[str] = Field(None, alias="returnUrl")
     metadata: Optional[Dict[str, Any]] = None
@@ -73,5 +73,5 @@ class TransactionResponse(BaseModel):
 class WalletBalanceResponse(BaseModel):
     wallet_id: str = Field(..., alias="walletId")
     currency: str
-    balance: str
+    balance: float
     mode: str