Authorize.net / do not do business with them

Be careful before starting using them. They are very sneaky and are glad to cheat you.
They have lots of additional and hidden fees, so your total monthly payment may be different from the expected one.
They charge you without any notification, without explanations. For something you never requested. If you complain them about it, they will only blame you and hang up on you.
Beware, buyers.