For the past 3 days around 11am, these two people keeping parking in my driveway, walk up to the front door, knock and ring the doorbell stand there for about 5 minutes and leave. We don't answer it because for one we don't use the front door (we use the back), and two, we don't know who the forget it is. The first day it happened I wasn't at home, only my Mom was. My Mom said she didn't bother to check who was at the door, but she said she saw it was a white car. Yesterday, a different car pulled up, and two men in suits with briefcases got out, knocked on the door very aggressively, waited a few minutes, then got in the car and left. It's really scary because they could of seen me in there. Let me draw a diagram;

They haven't showed up today, and if they do I'll try to take a picture. Ironically, about a week ago some anonymous number called our house phone. Here is the conversation:
Hello is this [insert Mom's name here]?
I'm not telling you anything. Who is this?
You paid for medications online, you need to pay now.
I'm sorry, I don't know who this is, but I'm hanging up now.
YOU NEED TO GO TO COURT, NEW YORK CITY.
Please stop. Goodbye.
FIND AN ATTORNEY!
It went something like that.
It's really creepy and I don't know why this is happening. Any ideas?