Read that if it is a robocall and you talk it registers that the number is legit, they then onsell the number. Not sure if this is correct but just in case if I dont recognise the number I dont speak till the caller does. Since using this strategy I do get less spam calls.

Three phone rings and they hang up. Strange. What's the point?

Three rings and they're gone

Caller: Open Agent - Real Estate Company

Cold Called. Rang back and it's the above. Telemarketing

Hangs up when answer

Hung up as soon as I answered