Which AT&T cell phones allow the maximum number of texts?

I have the LG Xenon and am disgusted with the 150 text message limit. I am constantly having to delete messages because I run out of space. The problem is I'd like to keep some of these messages, either for personal or practical reasons. My previous LG phones(all flip phones), all allowed me to hold hundreds of texts. And I sometimes had texts going back a full year or even longer. That's another thing I hate. As far as I can tell, there is no deletion protection on this phone. Sure, you move messages to the mem card, but if you decided to delete all messages at once, it will delete all messages whether they're on the phone or the mem card! So I want to get another phone. I'd like a phone like the Xenon, something with a touchscreen, qwerty keyboard, and for AT&T. But what phone out there allows a high number of texts?