Just had a random thought.
Not sure if this has been spoken about yet. So sorry if it has.
May be worth for something to test and to help Mondo to block/prevent this.
Can you topup with a Curve card but with the credit card linked?
As it would allow free cash withdraw with credit cards. Kinda defeats the point as I belive the Curve card allows free cash wishdraw from credit cards anyway.
Just a thought!