Receivables Performance Management / RPM Payments

I was called by an rpm rep claiming to be collecting a debt by sprint. He told me that i owed sprint $292.00 for a past due cell phone bill and that if i paid $168.00 total that my service with sprint would be restored within 24 hours. I told the rep that i had planned to pay sprint direct after i moved because i just recently began working again after a 9 month lay-off. The rep then told me that i had to pay today to have my services restored at that discounted price so i payed with my debit card. I then called sprint and they told me that it was just one of their third party tactics to get me to pay on an account and basically laughed at me saying well you still have to pay the remaining balance. I will never in life deal with sprint again due to their quote "third party collector" in fact i will do everything in my power to encourage a boycott on sprint!
Is that way of buisness even legall