no one on the line when I answered

same here

no one was on the line when i answered

where is this number?

I keep getting calls from their Automated System saying my Car's waranty is about expire, and they want me to sign me up for an extened warranty.  When I push "1" to talk to a representative they say they represent the "National Underwritters" something or other.  When I ask what company do they actually work for they hang up.
I want to get them to stop calling, but they hang up before I can tell them to put me on their don't call list.
If I call the number, it goes to an Automated System and says to enter a phone number to be added to a don't call list, which I do.
But the calls still keep comming.