Scam and Phishbusters → [Scam] Preferred Platinum Plan

I've been targeted by "Preferred Platinum Plan" for a $200 scam relating to "Adult Calls" that I have never made. They have been sending bills and letters for months saying that I owe them money. If you do a quick google search you can see that they are a bunch of crooks. I'm guessing that they don't actually have my phone number (even though they claim I used it to make calls) since they have never called. Also, all my bills/utilities are under my full name and this is sent to my nick-name, which I never use for anything official.

The past few letters claim that they will be sending it to collections. Haven't seen anything on my Credit report. I haven't called them based on other user experiences for harassment and I don't want them having my actual phone number.

I have no intention of paying these and will continue to ignore the bills. I was wondering though, since I'm getting this via US mail, could I submit it for Mail Fraud? I've thought about getting a Cease and Desist, but figure it is not worth my while.

Also tried doing a return to sender to the letter, but the post office keeps returning them to me.

If anyone wants to do some digging on them
Preferred Platinum Plan
PMB 711
7657 Winnetka Avenue
Canoga Park, CA 91306
877-775-1135

And my favorite little tidbit if you supply a credit card number to them "My Signature above authorizes future transactions to be charged directly to the credit card indicated above"