My user name ***********, but I am facing issue in add on of 500 users large meeting

[J-Zoom-ATL]

@asheeshbajaj If you are having issues purchasing the Large meeting add-on 500, you will need to reach out to our Billing support team via the methods in the article below. 
https://support.zoom.us/hc/en-us/articles/4405333397261-Zoom-billing-support

If you are having issues assigning licenses, you can do so as an admin/owner by logging into your Zoom web portal, visit the User Management -> Users tab, and then click on "Edit" next to the user needing to be assigned. 
Reference: https://support.zoom.us/hc/en-us/articles/115004976063-Assigning-a-License

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