[Mal]

I'm not sure you will have any luck trying to change Citibank's mind.

However, how I would approach this is to write a letter to "IG Markets" letting them know that Citibank are (possibly) restricting their trade by blocking their members and their transactions.

In addition, perhaps Citibank and slurring their good name by classifying them as "gaming" rather than an investment company.

They may choose to take this up with Citibank themselves. They would have great strength in a situation like this.