They called you before your son hoping you would get all flustered, contact him in a panic, and create false shame. Better still, you could scold your son into "coming out of hiding" on the pretense he cannot be found. This is a well worn collection tactic, deceptive and illegal under FDCPA. If you're in a Canadian province you should have a similar regulation.
This is Assett collections. Rebecca worked with me great. I had no problems with her. Now she is Gone and the others are rude. I wish she was still there until my final payment. 3 more months!!!!