Thank you sadinca for your help.
The responded to the BOP without objection. They included a statement with a zero previous balance ending in the current amount owed. What's weird is that the first transaction shows a date of May 2014 and the only payment made was also in May. The last statement was in December 2014 which means that the account (according to their statements) was only open for 7 months with only one payment being made. But they didn't send any of the other things I asked for but state the typical "Plaintiff reserves the right to amend this bill of particulars at such time as any other statement showing transactions are located."
As far as the joinder goes. I have been doing a lot of research and found basically that if someone is going to be sued and you will be personally affected by it, then you can request to be joined as a plaintiff or defendant. I have looking and looking and have not found a specific form but the law is there. (here is a snip of what I have found, forgive if it's too long).
Joinder is either compulsory or permissive.(2) It is compulsory if the court cannot give complete relief unless the parties are joined, if the judgment might prejudice the rights of the non-joined parties, or if other parties would be exposed to the risk of liability if the parties are not joined.(3) In short, a party must be joined when the court cannot render a fair adjudication without that party. For example, if family members have an undetermined interest in the same fund, the judgment obtained by any one party for part of the fund would necessarily determine the amount remaining available for the others, so all family members with an interest in the fund need to be part of the judgment.
Ironically enough I just found through wiki that you simply must use a pleading form to submit a motion for joinder and give the reason why. So I may have found how to do it. Either way I will continue with the discovery and all that other good stuff to maybe have them back off and drop it.