Yes, it's a mistake. Should be 'is' as it is referring back to information (singular). To use 'are' they should've rewritten the sentence to something like this: "Your bill, individual service charge details, and account history are available here together with additional information."

They refer to all three parts, not just additional information, that's why it's plural - are. If it was just about information, it would be written as: "Additional information is available here".

OK ... it seems like it should be "is", but the structure they have in mind is a subject in three parts, "Additional information .... " , "individual service ... " and " your account ... " - so the three elements together make a plural. It does read uncomfortably, though. It's just as easy to read it as ""Additional information (in three parts) ..." which would then take an is. I don't like it. I don't think the "additional information" needs a definite article, though - it's not the only possible additional information :)