Thanks for the good question! Crypterium at the moment of cryptofiat transaction requests user's crypto balance and acknowledges that there is enough crypto. Then we instantly transfer our fiat to merchant in the required sum and withdraw user's crypto at the current best rate (for the user) + commission of 0,5%. We will use our special technology CrypteriumSX (Smart eXchange) to find the best rate for you. More information about CrypteriumSX you can find in our White Paper (see section 3.1.1 https://crypterium.io/wp). Commission of 0.5% goes to buying CRPT tokens from the market and subsequently burning them.
User can preselect such an option as which cryptocurrency to use, perhaps in different percentages depending on their current trading value.
So, Crypterium does all the communication and payment in fiat without the user having to do anything other than bring up their smartphone to the NFC terminal and press go. Only the exact amount of tokens in the order and ratio prescribed are exchanged to meet the payment needs.
And what are the merchants' fees?