Taobao sells that kind of pure internet traffic card, but it can't make phone calls and send text messages. What kind of card is this? What's the network speed?

There are many such cards. The one you are talking about should be an infinite flow card. The signal is not particularly good. Of course it has something to do with your local signal. If the home signal is good, it will not affect the use. If the signal at home is not good, it will not work well. Need to look at it in light of its own situation. . . . Moreover, the unlimited flow card is not really unlimited. Generally more than 30, 40G will limit the flow. When it exceeds 100G, it will severely speed limit or automatically disconnect the network. It depends on what package you choose. The unlimited flow card I use can reach 7M per second at home and 1M per second outside, but there is almost no signal in some places. Whether it works or not depends on your local situation.