Multiple calls all day and night. Does not leave message. When I call back, they don't know what I'm talking about. I'm very annoyed.

THIS SCUMBAG HAS BEEN CALLING ME EVERYDAY AND HANGING UP, SO I CALLED HIM BACK., AND TOLD HIM IF HE EVER CALLS ME AGAIN I'LL HUNT HIM DOWN AND KILL HIM. I DOUBT THE SOB WILL BE CALLING AGAIN. TIME THE REST OF YOU START TO STAND UP FOR YOURSELVES I SURE [***] HELL DO.

This number called me during school, thankfully my phone was on vibrate. They left me a voicemail, and it was a loud sound that hurt my ears. This is the first time I get a call from this person.

i received 2 calls on 3-30-15 and a call on 3-27 and 3-24-15 from these scum bags, just hit ignore and don't answer :)

If it's the well-known CALLBACK SCAM then you did exactly what they want you to do.
ALLL they want you to do is COMPLETE THE CONNECTION, then they can plant their malware in your cell phone or your digital home phone. They cannot plant the worm/virus if you don't pick up, and they cannot plant it via VoiceMail. They need YOU to complete the connection, either by picking up, even for a second, or by CALLING THEM BACK.
Then the worm is planted in a millisecond, and they get every shred of data in your phone's memory.
Standing up for yourself means fight back SMART. It does not mean jump up & let 'em shoot you in the face.