Okay, so this is unrelated to what was initially posted.
After the first equipment change or first platform change, that whole replacement path is clearly futile, too.
Which means your assumptions on what is happening here are wrong. Clearly, and repeatedly, wrong.
Whether this is exceedingly well-funded adversary and beyond what help can be offered here, or there are other factors.
What steps have you already taken past the (obviously futile) replacements? Reviewed the carrier bills for, for instance, unrecognized or repeated numbers called?
Cases of my acquaintance have included the reporting person themselves making the changes, and forgetting making the changes. Other cases have had others with access to the device and its passcode, and gaslighting about their activities. Sharing or re-using or compromised credentials factors into yet other cases.
There are yet other possibilities. A compromise at Verizon or of a still-active (lost, stolen) device, certainly looks possible here, particularly if you have other (and unrecognized) phones associated with your account.
But. None of this is going to get solved here, or solved by calls to support either, whether this is an immensely well-funded adversary, or gaslighting, or some other cause entirely. Or solved by reading telemetry. We can’t ask — and you wouldn’t and shouldn’t answer — the sorts of personal risk and tech and security and account-related and other questions that would be involved in a discussion here, too.
