The same thing just happened to me! I called back but there was just beeping. If you reverse look up the number then it will tell you it's from Los Angeles, California somewhere on West 24th street but that's all the info i can get for now. And the monkey app is an app where you can video chat with strangers. It's probably the company trying to get people to download the app
DO NOT CLICK THE LINK, don't respond, nothing. These are specifically for people who are addicted to social media. If you're an adult, you don't care if somebody was speaking about you (even though they weren't). Don't get doxed, don't reply, don't click the link. Thats how people get robbed or worse.