I want to keep my unlimited data plan. Do I have to buy my phone from Verizon?

My original google nexus phone is struggling to be an effective device by current standards. As much as I want to keep it, I fear it's gonna give up soon. Do I have to purchase a new smart phone (full fare) from Verizon directly to keep my unlimited data? Can I purchase a new/used Verizon compatible smart phone from a friend/ebay/etc? If my current SIM card isn't compatible with the new phone (micro vs nano), will Verizon provide one and allow me to keep my unlimited data? I searched and found only threads that touched on this subject in pieces.

TIA

Accepted answers

Tidbits

Yes you can purchase a new or used Verizon compatible device outside. Keep in mind don't take any form of subsidization to keep your unlimited.

All comments

Tidbits

Yes you can purchase a new or used Verizon compatible device outside. Keep in mind don't take any form of subsidization to keep your unlimited.

Weth

And they will give you a new SIM free (at corporate store) to fit your new phone and still keep unlimited. Just make sure you are very clear you want to keep your unlimited and check the status of the account right away, even in the store.

ocd

Thanks for chiming in guys. I'm gonna go ahead and buy a used verizon phone and go for it. I'll update my post with the results after I go to the corp store.