Called, left no message

It is 2pm and today alone they have called 6 times.  Automated message saying I've been pre-approved for a student loan.  I got connected through to a human and told them to take me off their call list and they hung up on me

On Friday, July 14, between 12:00 noon and 3:48 pm, they had called me 6 times. I was working, so my phone was on silent. After they called that many times without leaving a single message, they passed spam call to harassing call. This particular number is now blocked.

Called me several times a day for a few days, and they always ring four times and quit. If I answer they hang up.  I had to shut my cell phone off for a few days to get it to stop (I hope).