Only text, calls, and map work on data when not on WiFi (iPhone 16, iOS 18.1.1)

I recently moved from an iPhone 8 to an iPhone 16 so I am new to 5G. I did not realize that it defaulted to using 5G over WiFi so it ate up the allowed 5G usage on my limited data plan very quickly. After 5G was no longer available for me, my phone stopped being able to utilize data on most applications, even after switching my data settings from 5G to LTE. Now, only text, calls and my map works when I'm not on WiFi. Most significantly, this means I cannot use a web browser, such as Safari, when not connected to WiFi. Please help.