I hope you are doing well. I am not as knowledgeable as Joey on this. But, I can think of 3 possible reasons of why this is happening.
1. Your wireless internet is not password protected, making it accessible for anyone. Here is a link to a tutorial I found for you to set it up:
2. Someone hacked into your network, to mess with you apparently. So, you will need to make your security stronger. But in this case someone else can assist you better than I can.
3. You gave your wireless password to a neighbor or someone when they went to your house. And now they are just having fun with you. So my suggestion would be to change the password on the wireless internet.
I hope any of this help.