diff --git a/CHANGELOG.md b/CHANGELOG.md
index d1a295dd..c54718b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Removed `withCarbonOffset` parameter from `create`, `buy`, and `regenerateRates` functions of the Shipment service as EasyPost now offers Carbon Neutral shipments by default for free
 - Fixes a bug where the original filtering criteria of `all` calls wasn't passed along to `getNextPage` calls. Now, these are persisted via a `_params` key on response objects locally
 - Removes the undocumented `createAndBuy` function from the `Batch` service. The proper usage is to create a batch first and buy it separately
+- Renames `primaryOrSecondary` to `priority` to match the API name for the parameter
 
 ## v6.9.1 (2023-11-20)
 
diff --git a/lib/EasyPost/Service/BetaReferralCustomerService.php b/lib/EasyPost/Service/BetaReferralCustomerService.php
index 65b4eba7..1b48277f 100644
--- a/lib/EasyPost/Service/BetaReferralCustomerService.php
+++ b/lib/EasyPost/Service/BetaReferralCustomerService.php
@@ -20,16 +20,16 @@ class BetaReferralCustomerService extends BaseService
      *
      * @param string $stripeCustomerId
      * @param string $paymentMethodReference
-     * @param string $primaryOrSecondary
+     * @param string $priority
      * @return mixed
      */
-    public function addPaymentMethod($stripeCustomerId, $paymentMethodReference, $primaryOrSecondary = 'primary')
+    public function addPaymentMethod($stripeCustomerId, $paymentMethodReference, $priority = 'primary')
     {
         $params = [
             'payment_method' => [
                 'stripe_customer_id' => $stripeCustomerId,
                 'payment_method_reference' => $paymentMethodReference,
-                'priority' => $primaryOrSecondary
+                'priority' => $priority
             ]
         ];
 
diff --git a/lib/EasyPost/Service/BillingService.php b/lib/EasyPost/Service/BillingService.php
index 9adfeaac..7db2980e 100644
--- a/lib/EasyPost/Service/BillingService.php
+++ b/lib/EasyPost/Service/BillingService.php
@@ -37,12 +37,12 @@ public function retrievePaymentMethods($params = null)
      * Fund your EasyPost wallet by charging your primary or secondary payment method.
      *
      * @param string $amount
-     * @param string $primaryOrSecondary
+     * @param string $priority
      * @return void
      */
-    public function fundWallet($amount, $primaryOrSecondary = 'primary')
+    public function fundWallet($amount, $priority = 'primary')
     {
-        [$paymentMethodEndpoint, $paymentMethodId] = self::getPaymentInfo(strtolower($primaryOrSecondary));
+        [$paymentMethodEndpoint, $paymentMethodId] = self::getPaymentInfo(strtolower($priority));
 
         $url = $paymentMethodEndpoint . "/$paymentMethodId/charges";
         $wrappedParams = ['amount' => $amount];
@@ -53,12 +53,12 @@ public function fundWallet($amount, $primaryOrSecondary = 'primary')
     /**
      * Delete a payment method.
      *
-     * @param string $primaryOrSecondary
+     * @param string $priority
      * @return void
      */
-    public function deletePaymentMethod($primaryOrSecondary)
+    public function deletePaymentMethod($priority)
     {
-        [$paymentMethodEndpoint, $paymentMethodId] = self::getPaymentInfo(strtolower($primaryOrSecondary));
+        [$paymentMethodEndpoint, $paymentMethodId] = self::getPaymentInfo(strtolower($priority));
         $url = $paymentMethodEndpoint . "/$paymentMethodId";
 
         Requestor::request($this->client, 'delete', $url);
@@ -67,18 +67,18 @@ public function deletePaymentMethod($primaryOrSecondary)
     /**
      * Get payment info (type of the payment method and ID of the payment method)
      *
-     * @param string $primaryOrSecondary
+     * @param string $priority
      * @return array
      * @throws PaymentException
      */
-    private function getPaymentInfo($primaryOrSecondary = 'primary')
+    private function getPaymentInfo($priority = 'primary')
     {
         $paymentMethods = self::retrievePaymentMethods();
         $paymentMethodMap = [
             'primary' => 'primary_payment_method',
             'secondary' => 'secondary_payment_method'
         ];
-        $paymentMethodToUse = $paymentMethodMap[$primaryOrSecondary] ?? null;
+        $paymentMethodToUse = $paymentMethodMap[$priority] ?? null;
 
         if ($paymentMethodToUse != null && $paymentMethods->$paymentMethodToUse->id != null) {
             $paymentMethodId = $paymentMethods->$paymentMethodToUse->id;
diff --git a/lib/EasyPost/Service/ReferralCustomerService.php b/lib/EasyPost/Service/ReferralCustomerService.php
index 37207d2b..17d4d62c 100644
--- a/lib/EasyPost/Service/ReferralCustomerService.php
+++ b/lib/EasyPost/Service/ReferralCustomerService.php
@@ -86,7 +86,7 @@ public function updateEmail($email, $userId)
      * @param int $expirationMonth
      * @param int $expirationYear
      * @param string $cvc
-     * @param string $primaryOrSecondary
+     * @param string $priority
      * @return mixed
      * @throws ExternalApiException
      */
@@ -96,7 +96,7 @@ public function addCreditCard(
         $expirationMonth,
         $expirationYear,
         $cvc,
-        $primaryOrSecondary = 'primary'
+        $priority = 'primary'
     ) {
         $easypostStripeApiKey = self::retrieveEasypostStripeApiKey();
 
@@ -114,7 +114,7 @@ public function addCreditCard(
 
         $stripeToken = $stripeToken['id'] ?? '';
 
-        $response = self::createEasypostCreditCard($referralApiKey, $stripeToken, $primaryOrSecondary);
+        $response = self::createEasypostCreditCard($referralApiKey, $stripeToken, $priority);
 
         return InternalUtil::convertToEasyPostObject($this->client, $response);
     }