Called and left no message. I called back to see who it was, and it is a survey.

Got a call from this number.  Didn't leave a message.  I called back.  A recorded message said something to the effect, "The Survey you are calling about has now finished." Then in very broken static, "Press... to be removed ... list...." Couldn't understand anything about the number to press to be removed, etc.  I tried calling the number from both my inbound lines. No difference. Likely a scam survey, since a legit one would have better quality and the survey wouldn't be over seconds after it initiated a call.

No message was left and I will not answer or return calls to unrecognized numbers

I agree with Anonymous, I called that number back and it did exactly what Anonymous, a lot of static and garbled talking and then nothing but silence and static garble.

Over the past several months I have received calls from 9 different numbers all of them starting with 817-580-7### none of which have been legitimate calls. I never answer calls from numbers I don't absolutely recognize. Most of these calls go to voicemail and leave no message. It seems to me to be scammers using a block of spoofed numbers.