When I called back it said thank you for Calling RPN I think, but I just hung up

They have been calling me none stop and I dont pick up.... How do we know if these calls from collectors are ligit? I dont want to pay them off if it is a scam, How do I protect myself from this?

Just keeps calling Sundays and all hours during the week even after 9pm! Won't say a word just sits on the line? Won't leave a message either when I refuse to pick it up.
Is there some way to put a stop to it?

They call me LITERALLY.. no [***] exaggeration.. about 6-10 times a day varying from 9am to 10pm. IT PISSES ME THE HELL OFF. This can make you borderline insane.. oh, and the kick.. SOMEHOW, SOMEWAY.. if my phone is on silent.. it rings for their number.. every time!!!! I hear it's just a fluke with my phone or service provider but it's really [***] annoying when you work nights and you get calls at 9am when youve been asleep for only like 3 hours.

Just got a call from them, but didn't answer.  With a name like Receivables Perf, I figure it's a collection agency.  They didn't leave a message.