With Visa it can only be done by entering long number etc. also enter their mobile number and a text is sent to their phone. There's a link in the text message that they click, opens the link in their browser where they confirm the payment and the app confirms the transaction there and then.
I got the bit wrong about money going into your bank account, it's actually 7 days, which although not ideal, it is no real hardship all things considered IMO.
2.75 % cost ie a £10 payment costs 27.5 pence.
The option/function where your customer 'signs' to confirm is not for Visa, Visa is text or email confirmation. That's why I suggested they have a data enabled phone, does it there and then.