I also received the collection letters after leaving Jones at the 30 month mark.  They hit me for the $18,750 charge.  Here's what I'd advise: 1.  Don't pay the money; 2.  Engage an attorney to write them a letter refusing to pay; 3.  Wait til the NASD arbitration letter arrives (it took about 18 months for that to happen); 4.  When you respond to the NASD letter the Jones attorney will call you; 5. Negotiate the payment, they were fair with me.

Because I went Independent and fundamentally changed the algebra on the payout scale...I would have been money ahead if I'd paid the entire amount they demanded up front, as it was I came out better.

Don't be consumed with the process, just go forward.  Things work out.