Interestingly, many public terminals/trade fairs over the globe use Quick Pay API to receive payments through mail, phone or password. As on April, 2018, 20,000+ customers/businesses are using it.
The admin is free to charge payment fee in either 'fixed' and 'percentage' manner and can set the title & configure payment fee tax if needed. Magento 2 Payment Fee Extension by MageComp helps store owners to transparently add payment provider fees or other payment charges on order subtotal.
