Is there a cheap way to get money from customers (Not PayPal etc)
PanMan: I think 4% is fairly small: A lot of payment methods ask more, ranging from 30% from Apple for in-app purchases, to 50+% for SMS payments. Here in the Netherlands we have Ideal, which mostly has fixed costs, but that is only attractive for bigger payments. When you have small payments, a fixed fee of E1,- isn't that nice...
In the end 4% isn't that bad, and for credit cards is hard to get under 2.5% - 4%, unless you have an amazon-like scale. I would also check how easy it is for customers to pay you: If you make 1% more, but lose 50% of your customers, that might be a bad deal (or it can be good, depending on your type of business).