org.hibernate.hql.internal.ast.QuerySyntaxException: Transactions is not mapped [select pl from Transactions pl]

Btw i currently develop a custom repository so i can select summary data by using filter from API. During development i got an error:

Springboot version: 2.3.3.RELEASE

org.hibernate.hql.internal.ast.QuerySyntaxException: Transactions is not mapped [SELECT pl FROM Transactions pl]

my entity class:

@Data
@Entity
@Table(name = "transactions")
public class Transactions implements Serializable {
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer id;
 @Column(name = "trx_amt")
 private BigDecimal trxAmt;
}

my repository:

   @RepositoryRestResource(collectionResourceRel = "transactions", path = "transactions")
    public interface TransactionsRepository extends PagingAndSortingRepository<Transactions, Integer>, JpaSpecificationExecutor<Transactions>,TransactionsRepositoryCustom{
    }

my custom repository:

@Repository
public interface TransactionsRepositoryCustom {
   TransactionReport getTrxAmtOnly(TrxFilter trxfilter);
}

my custom respository implementation:

@Repository
public class TransactionsRepositoryCustomImpl implements TransactionsRepositoryCustom{
    @Autowired
    @PersistenceContext
    EntityManager entityManager;

    @Override
    public TransactionReport getTrxAmtOnly(TrxFilter filter){
        Query totalAmt = entityManager.createQuery("SELECT pl FROM Transactions pl");
 return null
}