Why did my homepod make a phone call without my phone?

To be completely honest, I was watching Thor and I suddenly heard a ringing coming from my homepod. It was like an outgoing phone call to someone I have no idea would be on the other line. Once I realized it was my homepod, I unplugged the device. What could this mean and why is this happening? I am concerned about my privacy like everyone who buys Apple products. I checked every device in the house to see if there was an outgoing call but none was found. If someone is able to give me insight on why it did that and who it was to, it would be amazing. I care about the people around me and if people are listening through the homepod, that's a concern to me. I will not be plugging it back in until I find out more information on who it was calling. Please help.