Hi @Sushil_Pawa ,
You pay for the Workspace not for the base. i.e.: If you have 10 bases in one workspace, you will pay the same amount if you have 1 Base in your Workspace. That being said, the Owner of the Workspace is the one who will be invoiced. Your solution would be to Invoice the customer.
Please keep in mind that in case the customer collaborators does not need to enter data into the base directly or change something in the tables, you can always give them Read Only permissions which are not billable.
BR,
Mo