I believe this is one of Verizon's Collection Agency. They call and hang up and then they call you with a recorded message to stay on the line. Its all bs.  The funny thing is, I really don't owe them the money of 300+ dollars and I have even proven it to them. They are thefts and liars. If you still have Verizon, switch. Your better off down the road. Check your bills, They are constantly adding new fees.