iPhone 11: Mobile data switches to 2G, activation error

I have an iPhone 11, that is on iOS 26.2 but i have been getting a bug like, after sometime it switches to 2G/EDGE and only goes back to 4G after turning on and off airplane mode, then it has a problem where sometimes i get an error saying "Couldn't activate mobile data plan" i had before an iPhone 7 Plus and i didnt had that problem, is it a mobile data wrong configuration, a iOS bug or a carrier problem? When i restart the phone it goes back to 4G for sometime and then goes to 2G, also it started happening yesterday i had this iPhone 11 for like a month