How come I can text to iPhones but not androids???

I was getting charged for texts. I don’t have my notes from AT&T with me, to recall the name of the text charges. When I visited AT&T 12/2/21 to explain this problem, they had another customer there with the same problem. They called someone and it worked for a short time. Called last Friday still not working. I did what you suggested still not working.