Debt Collector Ignores Certified Letter/Cease Communication

[Guest-1667]

Hello, I am looking for some advice.
I was contacted by Universal Fidelity LP from Houston Texas by mail dated 12/1/07. The letter claimed I owed Chrysler Financial $320.25, which is totally false. I have never been contacted by this creditor in any format regarding any such debt.
I immediately mailed a letter to Universal disputing the alleged debt, and requesting that it be verified. That letter was dated 12/10/07, well within the 30 days mandated by the FDCPA. They ignored that letter and continued calling every week at all hours.
I mailed them a certified letter dated 2/4/08 directing them to immediately cease communication with me, and advising them that under no circumstances would I pay any alleged debt that was in fact false, and that I would not deal with them either over the phone or otherwise. They also ignored that letter and continue to call every week at all hours. I have the certified mail receipt, which was signed for at their Houston office on 2/12/08.
It appears that Universal Fidelity is in violation of the law, both by ignoring my written request that the alleged debt be verified, and by ignoring my certified letter directing them to cease communication with me.
Can anyone help, or offer advice?
Thanks