Who called from 2135503111

Just got call on cell phone.  Hung up when answered.

Missed call from this number 12minutes ago.

They hung up when I answered call

I've had 3 calls from this number.  The say nothing & hang up after 10 seconds. My number is registered on the Do-not-call list.  How do I report them or even find out who they are?

You can report any violations to the "Do Not Call Registry" on their website:

https://www.donotcall.gov

Just click on the "File A Complaint" link on the left-hand side of the website.