Here's how you trade Pokemon over the internet via GTS:
- Go to Jubilife City
- Go to the Global Terminal.
- Head to the north-western counter
- Deposit Pokemon in the GTS
Here's how you trade Pokemon with yourself (you need 2 DSes)
1. Insert the game you want Phione in one DS, and the game that has Phione in another.
2. Go to the second floor of any Pokemon Center
3. Talk to the lady that trades over Infared connection on both DSes.
4. Connect both DSes and trade Phione over.