If the phone is getting an address of 10.0.7.whatever, it is being provided to it, if the phone is set for DHCP discovery. Te phone system won't hand out an address unless the DHCP server is enabled.

Test a phone like this, assuming you have a power brick for the phone. Remove the network connection from the MBU. Plug a phone, set for DHCP into the bottom 8P8C jack on the MBU. If you have the internal DHCP server disabled, the phone shouldn't boot up. Then set the phone for static IP, set an address in the phone system's subnet and see if it connects. Do your wireshark traps looking for the 10.0.7 addresses. You shouldn't see any.

Can I get a copy of your data base?

Sometimes the thoughts in my head get so bored, they go for a stroll through my mouth. This is rarely a good thing.