I have gotten calls like that as well. Some voice recording saying they need to serve papers or something. I block that number then a day or so later the same voice recording same women calls from a different number! Wht the heck??!!
This number has been calling me several times a day over the past two days. They always hang up when the machine picks up. I have now blocked their number.
I'm blocking this number because they call many times a day. I suspect they are developing a database of when you answer your phone, which they can then sell to telemarketers who, obviously, would like to know what time of day you are likely to pick up the phone. The "survey" sounds like just a bogus excuse in case you do ask them who they are. They don't need to talk to you, as a machine can register the time they rang you and whether or not the phone was picked up.