Curve supports the following currencies:
GBP, EUR, USD, CNY, JPY, HKD, NZD, SEK, ZAR, NOK, BRL, CAD, ILS, CHF, SGD, INR, RUB, AUD, BGN, CZK, DKK, HRK, HUF, ISK, PLN, RON.
You can still add a payment card that uses a different currency but your card will be charged in GBP. This means there'll be more fees from your bank for spending in a different currency.
To avoid this, make sure your payment card is in one of the supported currencies above.