How do I disable xfinity wifi?

I am not sure if apple can help me solve this, but I would appreciate anyone's input

Over the past couple of months, I have found that my macbook air mini and ipad automatically join xfinity wifi where ever it is available. I do not have an xfinity account, and cannot access this, so it just blocks me from proper internet usage. I keep on setting my default back to my home wifi (which works just fine, and has been for the past 2 years), but every time I turn on the computer, it just goes back to non-working xfinity. Frankly, I am getting quite tired of having to go through this process every time I turn on my computer. Does anyone know of any way to fix this?