repetitive calls with no answer

calls several times a day. i try to call back and it syas not a valid exchange

calls several times a day. i try to call back and it says not a valid exchange

Same as the other people posting about this no ext you can't call back

They told me that I request info on some green thing and I told the guy I never heard of them so he just hung up on me. Since then that number has been calling every 30 mins and when I answer they don't say anything. When I called them back to tell them they didn't have to call every 30 mins, I was told that was a nonexisting ext.