Charge someone else's phone bill to let others know that I did it, and I want to send him a text message to find a euphemism.

What's so embarrassing about you helping others pay their phone bills? In fact, it's too late for the person who was charged to thank you, because he was charged for no reason, so he likes you very much. The so-called smiling face person, what is a smiling face person, is that you are good to me and everyone is good. He must be very happy that you charged him the phone bill. At this time, he will be very happy if you just send a text message. You can say that;

I have paid your phone bill. I hope I can help you and let you feel the help I brought you in this cold winter. Don't be too grateful. As long as we can understand each other, our friendship will last forever, there is no need to talk nonsense!