Invoices for every charge made are automatically sent to your billing e-mail registered with the subscription. Looking by "Manychat Invoice" and the name of the page, you can find them for every account you've upgraded using your e-mail:
If some invoices are missing in your e-mail inbox, you can find them through Manychat Settings ⇒ Billing ⇒ View Billing History. Each invoice can be downloaded through Ctrl+P (print current document) and choosing "Save as PDF".
