I have an iphone 12 pro and since yesterday I am getting intermittent “No sim available” alerts on my phone and no service. I have tried restarting my phone, checking for updates and taking out and putting my sim card back in. Is this an apple iphone issue or a Tmobile sim card issue?
Try removing the SIM and cleaning the metal contacts on the SIM with some Isopropyl on a papertowel. If the SIM is a few years old or older. It might need to be replaced.