Answered the call and got a recording thanking ME for calling THEM.  "All agents are currently busy but if you hold...."  The recording didn't identify the caller or the reason, so why would I hold????

i have no idea who and how they got my number

This number calls me from time to time but I never answer it because I have no delinquent debts. I assume its cold calling

This number has been calling me the last 2 weeks, and they never leave a message. If it's so important to keep calling, why not leave a message? Therefore, I continue ignoring it because it is a recording.

This number is belongs to Xcel Energy. Collections. If you are behind on you electricity bill, this is why they're calling you.