It's my understanding that sim cards are universal with gophones. My experience is that I had a cheap basic Motorola gophone and upgraded to a Nokia 2610 (not expensive but I can check email with this phone, unlike the Motorola), anyway my daughter told me that instead of getting a new number and buying more time (since I had existing time already on the Motorola) just to take the sim card out of the Motorola and put it in the Nokia. I did and it works like a charm, it kept my existing address book and the time I had left from the last time I bought minutes.
