diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/Accounts.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/Accounts.java
index 5f211eebd..18a797c5e 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/Accounts.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/Accounts.java
@@ -27,6 +27,7 @@ import org.whispersystems.textsecuregcm.util.UUIDUtil;
 import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
 import software.amazon.awssdk.services.dynamodb.model.CancellationReason;
+import software.amazon.awssdk.services.dynamodb.model.ConditionalCheckFailedException;
 import software.amazon.awssdk.services.dynamodb.model.Delete;
 import software.amazon.awssdk.services.dynamodb.model.GetItemRequest;
 import software.amazon.awssdk.services.dynamodb.model.GetItemResponse;
@@ -38,6 +39,8 @@ import software.amazon.awssdk.services.dynamodb.model.TransactWriteItemsRequest;
 import software.amazon.awssdk.services.dynamodb.model.TransactionCanceledException;
 import software.amazon.awssdk.services.dynamodb.model.TransactionConflictException;
 import software.amazon.awssdk.services.dynamodb.model.Update;
+import software.amazon.awssdk.services.dynamodb.model.UpdateItemRequest;
+import software.amazon.awssdk.services.dynamodb.model.UpdateItemResponse;
 
 public class Accounts extends AbstractDynamoDbStore {
 
@@ -302,11 +305,10 @@ public class Accounts extends AbstractDynamoDbStore {
 
   public void update(Account account) throws ContestedOptimisticLockException {
     UPDATE_TIMER.record(() -> {
-      final List<TransactWriteItem> transactWriteItems = new ArrayList<>(2);
+      final UpdateItemRequest updateItemRequest;
 
       try {
-        final TransactWriteItem updateAccountWriteItem = TransactWriteItem.builder()
-            .update(Update.builder()
+        updateItemRequest = UpdateItemRequest.builder()
                 .tableName(accountsTableName)
                 .key(Map.of(KEY_ACCOUNT_UUID, AttributeValues.fromUUID(account.getUuid())))
                 .updateExpression("SET #data = :data, #cds = :cds, #pni = :pni ADD #version :version_increment")
@@ -322,32 +324,21 @@ public class Accounts extends AbstractDynamoDbStore {
                     ":version", AttributeValues.fromInt(account.getVersion()),
                     ":version_increment", AttributeValues.fromInt(1),
                     ":pni", AttributeValues.fromUUID(account.getPhoneNumberIdentifier())))
-                .build())
-            .build();;
-
-        transactWriteItems.add(updateAccountWriteItem);
+                .build();
       } catch (JsonProcessingException e) {
         throw new IllegalArgumentException(e);
       }
 
       try {
-        client.transactWriteItems(TransactWriteItemsRequest.builder()
-            .transactItems(transactWriteItems)
-            .build());
-
-        account.setVersion(account.getVersion() + 1);
+        final UpdateItemResponse response = client.updateItem(updateItemRequest);
+        account.setVersion(AttributeValues.getInt(response.attributes(), "V", account.getVersion() + 1));
       } catch (final TransactionConflictException e) {
 
         throw new ContestedOptimisticLockException();
 
-      } catch (final TransactionCanceledException e) {
-
-        if (e.cancellationReasons().size() > 1 && "ConditionalCheckFailed".equals(e.cancellationReasons().get(1).code())) {
-          log.error("Conflicting phone number mapping exists for account {}, PNI {}", account.getUuid(), account.getPhoneNumberIdentifier());
-          throw e;
-        }
-
-        // We can infer an optimistic locking failure if the UUID is known
+      } catch (final ConditionalCheckFailedException e) {
+        // the exception doesn't give details about which condition failed,
+        // but we can infer it was an optimistic locking failure if the UUID is known
         throw getByAccountIdentifier(account.getUuid()).isPresent() ? new ContestedOptimisticLockException() : e;
       }
     });
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/storage/AccountsTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/storage/AccountsTest.java
index 217f658cf..96faa029c 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/storage/AccountsTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/storage/AccountsTest.java
@@ -40,6 +40,7 @@ import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
 import software.amazon.awssdk.services.dynamodb.model.AttributeDefinition;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
 import software.amazon.awssdk.services.dynamodb.model.CancellationReason;
+import software.amazon.awssdk.services.dynamodb.model.ConditionalCheckFailedException;
 import software.amazon.awssdk.services.dynamodb.model.CreateTableRequest;
 import software.amazon.awssdk.services.dynamodb.model.GetItemRequest;
 import software.amazon.awssdk.services.dynamodb.model.GetItemResponse;
@@ -329,7 +330,7 @@ class AccountsTest {
     device = generateDevice(1);
     Account unknownAccount = generateAccount("+14151113333", UUID.randomUUID(), UUID.randomUUID(), Collections.singleton(device));
 
-    assertThatThrownBy(() -> accounts.update(unknownAccount)).isInstanceOfAny(TransactionCanceledException.class);
+    assertThatThrownBy(() -> accounts.update(unknownAccount)).isInstanceOfAny(ConditionalCheckFailedException.class);
 
     account.setProfileName("name");
 
@@ -358,38 +359,14 @@ class AccountsTest {
     accounts = new Accounts(dynamoDbClient,
         dynamoDbExtension.getTableName(), NUMBER_CONSTRAINT_TABLE_NAME, PNI_CONSTRAINT_TABLE_NAME, SCAN_PAGE_SIZE);
 
-    when(dynamoDbClient.transactWriteItems(any(TransactWriteItemsRequest.class)))
+    when(dynamoDbClient.updateItem(any(UpdateItemRequest.class)))
         .thenThrow(TransactionConflictException.class);
 
-    Device device = generateDevice(1);
-    Account account = generateAccount("+14151112222", UUID.randomUUID(), UUID.randomUUID(), Collections.singleton(device));
+    Account account = generateAccount("+14151112222", UUID.randomUUID(), UUID.randomUUID());
 
     assertThatThrownBy(() -> accounts.update(account)).isInstanceOfAny(ContestedOptimisticLockException.class);
   }
 
-  @Test
-  // TODO Remove after initial migration is complete
-  void testUpdateWithMockTransactionCancellationException() {
-
-    final DynamoDbClient dynamoDbClient = mock(DynamoDbClient.class);
-    accounts = new Accounts(dynamoDbClient,
-        dynamoDbExtension.getTableName(), NUMBER_CONSTRAINT_TABLE_NAME, PNI_CONSTRAINT_TABLE_NAME, SCAN_PAGE_SIZE);
-
-    when(dynamoDbClient.transactWriteItems(any(TransactWriteItemsRequest.class)))
-        .thenThrow(TransactionCanceledException.builder()
-            .cancellationReasons(CancellationReason.builder()
-                .code("Test")
-                .build())
-            .build());
-
-    when(dynamoDbClient.getItem(any(GetItemRequest.class))).thenReturn(GetItemResponse.builder().build());
-
-    Device device = generateDevice(1);
-    Account account = generateAccount("+14151112222", UUID.randomUUID(), UUID.randomUUID(), Collections.singleton(device));
-
-    assertThatThrownBy(() -> accounts.update(account)).isInstanceOfAny(TransactionCanceledException.class);
-  }
-
   @Test
   void testRetrieveFrom() {
     List<Account> users = new ArrayList<>();