lower my bill

I need to know what my options are for lowering my bill. I have been with Tmobile since they were Voicestream. Over the years my bill has continued to climb to the point its become unaffordable. Sure I've added lines but its never as simple as an additional $10/mo. What am i doing wrong? Are there discounts I'm not aware of that I could use? It seems like every time I try to lower my bill it ends up being more. I'm not sure what to do anymore. I'm ready to bail on this whole arrangement if they can't find ways to make it more affordable. Maybe going with a cheap month to month prepaid phone for everyone in my family is the answer idk. Has anyone here had luck reigning in their cell phone expense or have any tips or tricks to suggest getting the most for your money here.