I don't really mind what it's called. Giving a lower than market rate for Bitcoin to Fiat conversion is an additional cost to the user that isn't mentioned on the web site.

To me, this is just as misleading as FX converters who advertise 'Zero commission' and then provide a terrible conversion rate to make up for it. They're trying to hide costs to the consumer.

Whether you want to call it a fee or not, it's a cost that is hidden unless the user looks into the BTC / Fiat rates elsewhere at the time of loading the card. The size of this additional cost makes it not worth my while using Wirex for now, as I can save money using Local Bitcoins & other exchange methods + my bank.

However, I can see that using Wirex would be simpler, so I'm sure there are many people who are willing to take the hit on poorer conversion rates in exchange for the convenience.