I didn't answer and they left a message saying "This message is for buyer, please give us a call back at-" and then left an 800 number.

This is Pioneer Credit Recovery calling to collect your student loan debt thru Sallie Mae / USA Loan Group.  They use an auto dialer and when you answer, the system detects your voice and immediately transfers the call to a live agent if one is available. If one is not, then you will get another automated call soon thereafter. This may go on all day and night.  The company employs those without scruples. They break all the federal laws regarding fair debt collection including making calls to your family members, employers, and neighbors in where they divulge you owe a debt to someone. That in itself is highly illegal. Do not answer their calls or you will get thrown quickly into their harassing nightmare.
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Caller: Pioneer Credit Recovery

Call Type: Debt Collector