I have the old unlimited talk, text, data plan. If I purchase a new phone from Republic Wireless I will lose my plan which is too bad. If I buy a used phone online such as the Moto G4 can I activate it with my number and keep my old plan?
There are used phones that would allow you to keep your grandfathered plan but it must be a Republic specific legacy phone (Moto E1, E2, G1, G3, X1 or X2). It cannot be a Republic 3.0 phone new or used. Republic 3.0 phones are these phones: Republic Wireless 3.0 Phones.
Guidance for acquiring previously used Republic phones here: Buying and Selling Used Republic Wireless Phones.