Oh gah... please don't listen to this.
I know you mean well, but you have two very simple things that you're confusing:
1. FDCPA DOESN'T apply to third party lenders. i.e.- Your auto finance company. You go to the dealer, and the dealer finances your car. Ford Credit (let's just say...) then buys the paper (contract) from the dealership. They're a third party lender. And THEY don't have to follow the FDCPA. I should know, I work for one.
2. The Mini-Miranda ("I am a debt collector...") only has to be stated in a few states. CT, the 5 boroughs of NY, etc.
As for the poster who said to write a letter: that's good advice. Write a letter stating that they may not contact you BY PHONE at your place of business or your home. If they do, then you have a case. However, don't expect them to phone you, because despite the poster's comments, companies DO take those things seriously. They don't want a lawsuit.
You're more likely to have a case based on the mini-miranda than anything else. Everyone forgets to say that.
Also, remember that no collector can contact you more than once a day, unless you request for them to do so.