They keep calling and hanging up,don't know why or what they want

I finally answered and got a recording that said, "This is not a sales call.  Please press 1 to talk to a representative."  What??? Why would I?  Stop calling me!

They keep calling me and I don't know why.

Have been getting calls from this number and random times. If I let it go to voicemail it just leaves a message about a system error. If I answer just get the same press 1 to talk to a representative as above.

They call several times a day while I'm at work and can't answer my phone.  There is almost always an automated message telling me to call back for "an important business message".  'Tell me who it is, or I'm not calling back' is what I'd like to say to them.