This is the content of the e-mail I just sent.  The names have been changed to protect the 'innocent' (namely me!).

I am such a wuss!

"Thank you (blank),

I assure you that I have not been slandering your company.

I apologize for the faxes - it was unfortunately the only way I could
obtain any sort of response from your company.  We simply wish to be
paid for the services that we provided.

I am at a loss to understand why you and (blank) would be upset with
us.  We don't owe you money from August of last year, we have always
responded to your e-mails and we have always tried to provide the best
service possible.

If there is a reason for not paying the invoices or if you need more
time I would be happy to come to some sort of agreement.

At the moment I am simply happy that after almost a year we are
actually communicating.

I will look forward to the check information and again, I am sorry if
you are upset."