Kinda yes and kinda no.
Your fanta account is registered to your device. So all the cards are all there and not going anywhere. But if you log into your account on a different device, eg an upgraded phone, you won't be able to trade or use the inbox.
If you use the same sim card, you might not run into this problem, if you do run into this problem then you may have to create a new account and trade all your cards to that new account.
Though remember, you have to be at least lvl 30 to be able to trade.