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My father's phone number was ported to another carrier. He didn't want that, but who knows what the other company said or did. In my option they were preying on the elderly. I am hoping that there is a way stop this from happening again by locking it down somehow. Is this kind of thing possible? Maybe require an additional verification step on the Cox side of the transfer so there is a double check before the transfer happens? When this happened, it took about a week to figure out why the phone stopped working, and then a week to get the number ported back from the other carrier so it was pretty frustrating.
Isn't this the whole reason Cox has a PIN? I would go after the other company for stealing the number without your permission. Does someone have your PIN? If so I would change it ASAP.