Please how can you prevent a shop attendant from seeing already created customer and their sales invoice on a new shop attendant’s account?
You cannot. Permissions allow restrictions to functional tabs, but not to individual customers. So if a user can see sales invoices, she can see all sales invoices. If she can see customers, she can see all customers.
Please what should I do since I don’t want the new shop attendant to get access to old records.
Nothing, you can not restrict this