Proforma invoice for TopUp

I have somehow switched to normal invoices being issued when doing a topup instead of a proforma.

If I want to delete a topup, the transaction is marked as read only,so I cannot directly remove that. I can delete the invoice, but the topup is still reflected on the user’s statistic.

Would it work if I switched back to proforma invoice for topup?

How do I switch back to proforma invoice for topups?

Thanks for an excellent product.