You need to send them a certified, return receipt debt validation, cease and desist calling, or "not me" letter (think of it as the best $6.47 you ever invested).  Also send it first class mail in case no one will sign for it.  Make a notation of that fact at the bottom of the letter.  You also need to report them to the proper agencies to which I have provided links to.  Then you need to go out and get a consumer lawyer to sue them on a contingency basis (no money out of your pocket) and let them pay you for the harassment.  If everyone did these three things, these crooks would be bankrupt and we would all be the richer for it.  Use these web sites to find an attorney in your state that will probably take the case on a contingency basis (no money out of your pocket up front):  http://www.consumeradvocates.org/
http://www.consumeradvocates.org/find-an-atto ... tates_value=All

Everything else you need to know follows including at least two agencies where you should report their criminal activities.

ACCELERATED SERVICING GROUP, LLC.
Number threads associated with these crooks:  http://800notes.com/Phone.aspx/1-716-382-7425
http://800notes.com/Phone.aspx/1-855-208-3523

Website indicates that they are located in western New York, world’s #1 capital for crooks pretending to be debt collectors:  http://asgllcny.com/contact-us/
BBB gives them a B- rating with 6 complaints and 1 negative review:  https://www.bbb.org/upstate-new-york/business ... le-ny-235972646
Interesting that I have 4 addresses for them already.
BBB: 2390 N Forest Rd Ste 7
Getzville, NY 14068-1294
Website: 550 N. Bailey Ave.
Amherst, NY 14226
Facebook page: 550 N. Bailey Ave. #200
Amherst, NY 14226
State registration:  1840 Highland Dr.
Tonawanda, New York 14150
New York Dept. of State info:
Selected Entity Name: ACCELERATED SERVICING GROUP LLC
Selected Entity Status Information
Current Entity Name:    ACCELERATED SERVICING GROUP LLC
DOS ID #:    3838376
Initial DOS Filing Date:    JULY 28, 2009
County:    NIAGARA
Jurisdiction:    NEW YORK
Entity Type:    DOMESTIC LIMITED LIABILITY COMPANY
Current Entity Status:    ACTIVE

Selected Entity Address Information
DOS Process (Address to which DOS will mail process if accepted on behalf of the entity)
ACCELERATED SERVICING GROUP LLC
1840 HIGHLAND DR
TONAWANDA, NEW YORK, 14150
Registered Agent
NONE


It is incumbent upon them under the law to prove that the debt exists and that you owe it, and that they have the legal right to collect it.  You are not obligated under the law to prove that you don’t owe or that it is paid.  

Federal law (FDCPA) requires them to send you a letter (US MAIL ONLY) postmarked within 5 days of their first contact that contains their name, physical address, the creditor’s name, and the amount of the alleged debt.  It also must contains “mini-Miranda” telling you that it is an attempt to collect a debt and that all information will be used for those purposes.  The one other important thing that this letter must also have in it is that you have a right to dispute the debt within 30 days of receipt of the letter and if you do so, all collection activity must be stopped until the debt is verified.

Read up on your rights here and also make a complaint at this government site:  http://www.consumerfinance.gov/

Also file a complaint with your State Attorney General's office.
List of State AG’s offices:   http://800notes.com/faq/attorney-general

File a complaint at the NY State AG's Office here:  http://www.ag.ny.gov/