Here are various phone cards, spanning most of the age of phone cards. At the bottom, you have older cards, which were simple things, just colored plastic with the same image of Sonic printed on it at various sizes. The holes & numbers there are likely indicators of how much time was bought on it. Notice how most of them have 1 or 2 tiny round notches on the end opposite the 'in' end. The 2nd white card says "High-Tech Entertainment" the first is labeled as "Game Card", the yellow one says "Mega Drive Mega High Quality Computer Video Game" the one where Sonic has a microphone is all in Japanese...but it is rare/possibly the least common of all the cards seen here.
The upper card for Sonic R is by "Project Sonic" and says High Speed Action Packed Racing Extravaganza Taking off Into the Real 3D World" which is a bit complex for a slogan. The greenish center card uses old Japan only art (larger finger, taller eye) The yellow ring says "His Name is Sonic" The bottom card uses the early SA1 style art where he's riding the skateboard, and is by "TZone", "QUO" and "CSK-Net". It's slogan is "Come Ride the Highway" (Speed Highway?) & uses what looks like a screenshot from SA1 as its background.
Phone cards fell out of usefulness not long after SA1, as cellphones & their plans became more common, no one cared about kiosk or pay phones where you'd have to slip in a card like this to pay for the time. This makes the QUO card likely to be one of the last few they did. 

Discovered by QwertySonic