Unknown Calls and Phone Numbers

I bet most of you do receive unknown calls or those numbers that aren't save on your contacts.
I really wondet how does this caller got my numbers from.
Most of the time, the calls are from insurance company which I really hate!
Usually I don't answer those call but I'm afraid that I'll miss out important calls for me so I'll try to answer.

Few hours ago, I received a call from, I believe is from insurance company as she keep telling me about policies.
She speaks like a Filipino and I can hardly understand her spoken English.
I wasn't paying attention to her as I was not interested in what she's telling me.
Until the end, she asked for my particulars and I was wondering why.
So I doubled confirmed again and again.
Luckily I didn't give her my particulars as she gonna do enrollment for me.
At first, I sort of agreed to the enrollment because I can't understand her.
When I turned down her request, she asked me why.
What why? She said that there's no obligation what. Tsk!
In the end, I told her off that since there's no obligation and I'm not interested, I don't want to join.
I guess this is the first time I reject people directly like that.

So what do you think?
I know these people are trying to make a living as well and I really don't mean to be mean.
However, too much of these really pisses me off. Sigh~