This phone card was made for Sonic Adventure DX.
It is an uncommon card. It features a 'shatter effect' blue background, out of which CG art of Sonic is 'crashing through'. It has the game's logo in Japanese at the top, a word on the other side & the year 2003 Early Summer. The tiny text at the bottom is the copyright.
Because it says "early summer", does that mean that DX themed phone cards were released throughout the year some how, with different designs? It seems odd to label the card for the time of year, if it wasn't a part of something else. Because it's so uncommon, there's no much info on what this was a part of. (Meaning, a set of them, a give-away, some sort of bonus that came with the game, etc)