Instead of sending funds for a cryptocurrency purchase and waiting for the transaction to clear - and by extension risking that the exchange rate may change - you can first purchase a voucher, and then exchange it for cryptocurrency at any moment. This way you will be certain that you will be able to puchase cryptocurrency at the exchange rate from the moment that the voucher is activated.
If you have purchased a voucher, you can use it by clicking the link "Load Voucher" below