How do I keep my old land line phone number?

We got a device called "Home Phone Connect" from Verizon to replace our landline and then had our landline number transferred to it. It's actually a cellular device that you can plug a regular landline phone into. People that call can't tell that it's not our old landline.

We recently moved to a completely different area code and just moved the device with us. Plugged it in at the new place and it worked without needing to do a thing.