I keep getting 971 phone calls, the last 4 numbers being different with each call.  I never answer any number I don't recognize or if they don't leave a message.

I get a call from this number about every other week. This has been going on for several months. The caller ID says "unknown name". They never leave a voicemail, so I don't know who they are or what they want.

Calling that number back puts you into a call queue for a company called "Account Control Technology" which provides "specialized debt management and collection solutions".  I.e., they're debt-collecting [***].