Suggestions to improve query performance - sql

Question

I'm running the following query on our SQL Server DB.
The query takes at least 20 minutes to complete. I don't have permissions on the db to run execution plan
Thoughts or suggestions on what to try would be appreciated
SELECT
UsageDate,
--convert(date,dateadd(day, 22 - 1,dateadd(month,cast(datepart("MM", dateadd("d",-21, getdate()-2)) as int)- 1,dateadd(year,cast(datepart("yyyy", dateadd("d",23,getdate()-2)) as int) - 2000,'2000-01-01'))) ) AS BILLING_CYCLE_START_DT,
(sum(MVNO301TotUsg)-sum(ROAMING_3G_LTE)) MB,
sum(ROAMING_3G_LTE)ROAMING_3G_LTE,
case when convert(date,UsageDate) = convert(date,dateadd(day, 9 - 1,dateadd(month,cast(datepart("MM", dateadd("d",-8, getdate()-2)) as int)- 1,dateadd(year,cast(datepart("yyyy", dateadd("d",10,getdate()-2)) as int) - 2000,'2000-01-01'))) )
then 100000000 else 0 end as BeginBaseAvgMB
FROM
(
select convert(date,EVENT_DT) UsageDate,
sum((USAGE_KB_3G+LTE_USAGE_KB+EHRPD_USAGE_KB)/1024)AS MVNO301TotUsg,
0 ROAMING_3G_LTE
from [spmp].[dbo].SubscriberCombinedUsageallmvnos USG with (NOLOCK)
JOIN aMVNO.dbo.Subscribers S with (NOLOCK) ON USG.subscriberkey =S.subscriberkey
left Join aMVNO.dbo.exMVNOs_Realm_RISE RLM with (NOLOCK) ON S.SubscriberNumber = RLM.SBSCR_NBR
where (RESELLER_ID = 'a9')
and convert(date,EVENT_DT) between dateadd(d,-33,GETDATE()) and dateadd(d,-2,GETDATE())
group by convert(date,EVENT_DT)
UNION ALL
SELECT
convert(date,EVENT_DT) UsageDate,
0 AS MVNO301TotUsg,
sum(DOMESTIC_ROAM_3G + INTERNATIONAL_ROAM_3G +GSM_3G +ROAMING_LTE_KB)/1024 ROAMING_3G_LTE
from [spmp].[dbo].SubscriberCombinedUsageallmvnos USG with (NOLOCK)
JOIN aMVNO.dbo.Subscribers S with (NOLOCK) ON USG.subscriberkey =S.subscriberkey
left Join aMVNO.dbo.exMVNOs_Realm_RISE RLM with (NOLOCK) ON S.SubscriberNumber = RLM.SBSCR_NBR
JOIN [aMVNO].[dbo].[BusinessDate] BD WITH (NOLOCK) ON convert(date,USG.EVENT_DT) =convert(date,BD.DT)
where
(RESELLER_ID = 'a9')
and convert(date,EVENT_DT) between dateadd(d,-33,GETDATE()) and dateadd(d,-2,GETDATE())
GROUP BY
convert(date,EVENT_DT)
)Z
group by UsageDate
ORDER BY USAGEDATE