Can friends send messages to each other for free when they are offline (using Unicom mobile phones)? Can the other party see the message without logging in to the wing chat?

Yes, as long as you are on the wing chat, it is ok to send a text message or make a phone call to any mobile phone (whether the other party has a wing chat or not), and it is free, provided that both parties charge one-way (answering the phone is free). I am a mobile card. Give it to me with wing chat 5!

It's best to open 5 yuan GPRS, because using wing chat will consume a small amount of traffic (very little, which is the key point when dialing requests, probably less than 1K at a time).