Same number, yes. Same plan, no.
All 3.0 phones go on 3.0 plans. No Contract Cell Phone Plans without the hidden fees | Republic Wireless
If you buy the a GSM/CDMA phone from Republic, their computer will pick the best network for your area.
If you buy from anyone else or a GSM only phone, you will be put on TMobile’s network as of today. So make sure TMobile works for you by entering your address. Note when TMobile says a fair signal, you will have issues with your cell calls.
Additionally there are used Republic Wireless phones available if you want a 2.0 Plan. And comfortable with no warranty.