fixed wrong customer group that assign to order

Author: ProkopovVitaliy

app/code/Magento/Quote/Observer/Frontend/Quote/Address/CollectTotalsObserver.php

@@ -119,9 +119,7 @@ public function execute(\Magento\Framework\Event\Observer $observer)
 
         $groupId = null;
         if (empty($customerVatNumber) || false == $this->customerVat->isCountryInEU($customerCountryCode)) {
-            $groupId = $customer->getId() ? $this->groupManagement->getDefaultGroup(
-                $storeId
-            )->getId() : $this->groupManagement->getNotLoggedInGroup()->getId();
+            $groupId = $customer->getId() ? $quote->getCustomerGroupId() : $this->groupManagement->getNotLoggedInGroup()->getId();
         } else {
             // Magento always has to emulate group even if customer uses default billing/shipping address
             $groupId = $this->customerVat->getCustomerGroupIdBasedOnVatNumber(

app/code/Magento/Quote/Test/Unit/Observer/Frontend/Quote/Address/CollectTotalsObserverTest.php

@@ -243,26 +243,19 @@ public function testDispatchWithDefaultCustomerGroupId()
             ->will($this->returnValue('customerCountryCode'));
         $this->quoteAddressMock->expects($this->once())->method('getVatId')->will($this->returnValue(null));
 
-        $this->quoteMock->expects($this->once())
+        $this->quoteMock->expects($this->exactly(2))
             ->method('getCustomerGroupId')
             ->will($this->returnValue('customerGroupId'));
         $this->customerMock->expects($this->once())->method('getId')->will($this->returnValue('1'));
-        $this->groupManagementMock->expects($this->once())
-            ->method('getDefaultGroup')
-            ->will($this->returnValue($this->groupInterfaceMock));
-        $this->groupInterfaceMock->expects($this->once())
-            ->method('getId')->will($this->returnValue('defaultCustomerGroupId'));
         /** Assertions */
         $this->quoteAddressMock->expects($this->once())
             ->method('setPrevQuoteCustomerGroupId')
             ->with('customerGroupId');
-        $this->quoteMock->expects($this->once())->method('setCustomerGroupId')->with('defaultCustomerGroupId');
         $this->customerDataFactoryMock->expects($this->any())
             ->method('create')
             ->willReturn($this->customerMock);
 
         $this->quoteMock->expects($this->once())->method('setCustomer')->with($this->customerMock);
-
         /** SUT execution */
         $this->model->execute($this->observerMock);
     }