Unknown phone connected to my MacBook Air via Bluetooth

I clicked on the bluetooth icon to see why it was showing me the paired symbol and I noticed it was connected to a phone. No one in my home has a OnePlus 7 Pro, I can only assume it is a neighbor's phone.

I opened the bluetooth preferences because the menu bar gave me the option to disconnect and the first image is what I saw -that it was indeed connected to my computer. I clicked on the X to disconnect, which is the second image.

My questions are how was it able to connect to my MacBook Air and what can I do to prevent this from happening again? What are some of the consequences of this connection? For example, do I need to change any settings on my laptop?

I never gave permission to the device to pair with my computer. The phone disappeared from the device list after I closed and reopened bluetooth preferences. I keep bluetooth on because of my headphones/airpods and iphone.