How to trace an unknown/blocked/private number?

The past few days I've been getting numerous calls from a blocked number. At first it was just silence but now it's gotten obnoxious. When/if I answer they play this narwhal song...and if I don't answer they leave me the song as a voicemail. It's super annoying and I would like to know who it is but I need to find the number behind it. I am not willing to pay $4/month as some of these companies want me to because it is only the one caller who is bothering me. I use a smart phone but I am unsure how to use the *67 or 57 method on a cell phone. Please help!