how to set data limit for mobile data

Errm I just got my iphone 15 and my monthly data limit is 4GB so I want to set it to warn me at 3GB and stop it at 3.5GB and reset on the 4th. Is this possible? I could do it on every Android phone I've had since forever...It seems like the answer is no? What do people do? This seems like such a common thing people need to do. Do you all have unlimited data or something? WTF?