The DHCP is done via the ethernet MAC address. Most home routers have the option to clone the external mac address which would almost definitely give you a new ip.
Tier 2 reps don't have the ability to force an ip address change.
You need to either,
1) change the device the modem is connected to 2) note when your current dhcp lease expire and disconnect your modem for starting a few minutes prior to that time and leave it disconnected for a few hours past the renewal time.