My question involves collection proceedings in the State of: CA

A friend had contacted me and needed some money to put bail someone out. I agreed to pay part of the payment, and only the initial fee. My friend agreed to pay the monthlies and had also put down a collateral. The only document I signed was to authorize my first payment, and not the one allowing to draw a monthly amount or any other document in that matter.

I received letter in the mail asking for me to pay, but I am not the indemnitor or the co-signer and was under no promissory to pay the premium.- I only helped pay the partial one-time transaction. I had informed them via email about this error, and that I am not the one to be pursued or taken action against - I actually had been allowed not to sign some documents to allow such action, either.

Help me out here please. I believe the notice was in error. Did I miss anything here? What should I do?