We need 3rd party service provider who will do the uploading of the Beginning Balances of our books

Hello, @user6de495bf. I'll provide some steps on how to integrate a third-party app in QuickBooks Online (QBO).

Before we proceed, please know that not all third-party applications can be integrated with QuickBooks. To find out if a there's an available service provider who will process the uploading of the beginning balances to QBO, lets go to the Apps center. 
 

Here's how:

1. From the left menu, select Apps.
2. Head to the Find apps section.
3. Look for the app in the search bar or click the Browse category drop-down.
    

Once you're able to find the third-party app, you can go ahead and download it.

In addition, to ensure you're bank statements are always balanced and accurate, check out this article: Reconcile an account in QuickBooks Online. 

If you have further questions or concerns about third-party integration process in QBO, please let us know. We're always here to help. Have a good one.