How to prevent autoprovisining.

[ITdude87]

A local company recently went out of business. At the auction I bought their phones, Yealink T54W as I have a sip setup buy my phones are from the dawn of time. They keep autoprovisining back to the old companies service. And the service still works, I get calls for them if I leave it plugged in.

I have tried factory resetting them, installing new firmware and setting erroneous settings for autoprovisining but no matter what I do after a few minutes they go back to the old companies stuff.

I have gotten the phones to work on my sip setup but it only lasts a couple minutes before the settings are wiped.

Sense this is persistent across factory defaulting and firmware flashes I presume the phone are phoning back to Yealink with a mac address or something to get the old settings.

How do I fix this? I don't really want to wire shark and setup firewall rules and the like.