Calls 10 times a day. No one one line, no message left.

This is a collection agency using an autodialer that calls 24/7. They refer you to call back at 1-877-879-4512, stating they are open for business from 8am to 9pm in "all time zones".

It is Navient Student Loan Services.

Called a buch of times, no one on end of line when i pick up - blocked number on phone.

Had a call from this number two days ago, but no Caller ID name, and no message left.
If this is Navient, this must be their 'special' occasional use only phone number.  How many numbers do these creepy jerks actually spoof so their crimes cannot be documented or traced???