It should be possible to do so. There is no reason to use Simplex anyway, as they're fees are extremely high.
Try some of these exchanges (depending on your location): Coinbase, Coinmama, BitPanda or CEX.io.
Failed on CEX.IO as well.
I used my MasterCard on Cex.io a few days ago and everything works fine. Maybe there is an online spend limitation by the card-issuing bank. In this case, try Skrill and convert Skrill USD to the Bitcoin with services like Bitpanda and Wirex(service has high fees AFAIK).