They call upwards of 5 times a day, at least twice. They claim to be a collection company when they call, and they use a non-robotic sounding robot, so when you answer while they're leaving a message and try to tell them to stop, it's just a machine. If you try to answer when they call, they don't answer.
I've also noticed they only call between 9:30 and 2:30ish, due to the fact most people are at work between those times. As previously said, they hang up if you answer, or rather, don't start the automatic robot machine...thing. Very annoying.