As for an ITS, I do it similar to a complaint or affidavit by using numbered paragraphs.
1. On XX-XX-XX, this CA called my phone at XXX-XXX-XXXX
2. I spoke with XXXXXXXXX XXXXXX, who demanding payment in the amount of XXXX.XX
3. I asked for XXXXXXXXXX, and the response received was XXXXXXXXXXXx
4. This was a violation of U.S.C.XXXXXXXXXX
Etc, etc, etc. Stick to the facts, and only the facts.
PACER is the Federal Database. For a nominal fee charged to a credit card, it permits one to peruse complaints and documents related to their cases, that have been filed in Federal Court. It can be extremely helpful
I don't recall exactly, but I believe that one can opt to go through a lengthy application process to be exempt from payment. You should go to the Home screen, and google "pacer".
As for the rest of the answers, those are things you must figure out for yourself. You know your location, google your nearest Federal courthouse. Find their website, find their rules.
Have you not done any of this yet?