Spam calls

A quarter of a day ago (I was studying), they called numbers one after another and I just kept blocking them. They were calling from 12 in the afternoon until 6 in the evening, imagine that. Then in the morning, another number called like the others: 56, 57, 51. They scared me. Now when I checked the caller ID, I found they were just males. I want to understand if this is like a group where numbers are dropped or shared, or I didn't understand. Now, where should I go to complain? And I can't block these strange numbers because the new professors call me during study time.