Can't get my phone unlocked by Xfinity

It seems my phone is being held hostage as it only works for them. I bought my own phone paid in full, brand new before BYOD onto Xfinity Mobile years ago. I've moved and service at new home is spotty so I want to change to whatever everyone else in the neighborhood is using. First attempt to unlock, talking with an agent to unlock, it did not work. No email or explanation. Second time again on the phone with an agent, I end up hours later with a generic response with the email with link for conditions to unlock (I meet all the conditions). Third time, the agent tells me the reason is because of some other carrier has it locked before bringing it to Xfinity. However, it was bought brand new and I haven't had any other carrier. Its locked and I'm currently using it on Xfinity yet they cannot unlock it. I clearly can't reach out to anybody else unlock it. And yet after telling the agent this information, I'll continue to get the same response from the same agent like a robot. Can anyone help?