How do I change my cellular antenna?

My iPhone has been having trouble connecting to the cellular network. I have followed all the tips on the Apple website and still I can't connect to my network. I think that the cellular antenna is fried, so to say. I mean, it has been 3 days since I was connected to my cellular network, since then, it has said "Searching..." continuously. I noticed that there is a guide to replace the lightning connector and headphone jack where the antenna is mentioned, but there is no explanation as to how I can replace it. And just to specify, I don't care about the LTE cellular chip, my network doesn't support it yet, all I want to replace is the cellular antenna so I can connect to my network and be able to make, receive calls, send, receive texts and get data. Any kind of help is appreciated. Thanks!