American Credit & Collections How can they be so RUDE!! Scranton Pennsylvania

I recevied a voice mail message from ACC today, March 6, 2009 at 2:08 EST. I knew it was for me because he called me by my nickname. The message was - (nickname), you need to call me as soon as you get this message. My name is Lincoln Taylor, my number is 866-760-6205, extension 228. and slammed the phone down. That was all he said - no reference number, no reason for calling, etc.
At first, I thought that I would not return his call since he was so rude. But after some further thought & since I have gone through many disputes with all three of the credit agencies to clear up my credit report, I changed my mind.

Mr. Taylor was calling talk to my son. I told him he did not live with me anymore and had not lived with me for years. So he asked for his telephone number. I told him that I did not give out that information. He said you don't want to help your son? Of course during the course of our conversation, I was thinking, why am I even talking to this rude human? I told him not to call my house anymore and that this was harrassment. He told me to call 911 and ask for the police. Then I slammed the phone down.

Is it legal for a credit collection agency to call about someone else? And how do they get away with being so Rude and Obnoxious?

Cdc
Danville, Virginia
U.S.A.