Please advise, which of these services are better for a small business (Custom Essay writing service ? http://www.customessay.org) and did anyone use any of them:
it really depends on the merchant bank you choose. once you find a bank who provides you with an online gateway, then you need to get the documentation from them.
usually they have a set of variables you need to send to them securely via HTTP POST, and then they generate something you can parse to get responses.
once you have the documentation, it's a lot more clear.