df_by_plan = (df[(df.billing_reason != "manual") & ((df.status != 'draft') & (df.status != 'void'))]
              .groupby([pd.Grouper(key="created",freq="M"),"subscription.plan.id"])
              .agg(
                    {
                        "amount_due": "sum",
                        "amount_paid": "sum",
                        "customer_email": pd.Series.nunique
                    }
                )
             )
df_by_plan.rename(columns={"customer_email": 'customers'},inplace=True)
df_by_plan