credit card payment issue

[Remitur]

Unusual (and unwanted) behavior from WHMCS, using STRIPE module (but, I guess, it may happen with any other credit card gateway):

• user has no credit card registered
• user inserts an "add funds" order for 100 shells, but does not pay it; system issues invoice n. 300 (unpaid)
•  user inserts another "add funds" order for 100 shells, and pay it using credit card; WHMCS process it fine (100 shells credited to the user, invoice 301 (paid) is issued

So the invoice # 300 stays unpaid...

During the main cron /few hours later, during the night) the system process the payment of (still unpaid) invoice n. 300, using the credit card data used few hours before to pay invoice 301 (the credit card data has been registered by Stripe) 

  And so the user did TWO different payments, of the very same amount (one of them unwanted).

Any idea about how to prevent this behaviour?

[WHMCS Lawrence]

Credit would only be applied to an invoice automatically if the credit was present on their account during the invoice creation itself. If the client created an "Add Funds" invoice and didn't pay it until afterwards, the credit wouldn't be on their account and therefore wouldn't apply to the other invoice automatically.

The simplest option may be to disable the ability to add funds under Configuration > System Settings > General Settings > Invoices tab.

[Remitur]

2 hours ago, WHMCS Lawrence said:

Credit would only be applied to an invoice automatically if the credit was present on their account during the invoice creation itself. If the client created an "Add Funds" invoice and didn't pay it until afterwards, the credit wouldn't be on their account and therefore wouldn't apply to the other invoice automatically.

The simplest option may be to disable the ability to add funds under Configuration > System Settings > General Settings > Invoices tab.

The issue is not about "paying with credit", but about "paying with credit card" ...