Could you suggest me a free phone number generator service?

I need to sign up for a website to get access to some hard-to-find files. But that website demands my phone number to sign up. I don’t feel comfortable providing my phone numbers at all. So do you know any website that provide free fake phone numbers for verification?

Side question: does anyone know how to use textfree.us? I signed up for that site to get a phone number, but for some reason the phone number kept changing and I couldn’t get any verificafion message to comfirm my account.