SOS in right upper corner of 13Pro

This will be due to either the SIM card being broken or the SIM reader in your iPhone 13 Pro is broken. First try to re-insert the SIM Card using the ejector tool found in your iPhones box. if that doesnt work you could try to clean the SIM card using a dry cotten swab. if that doesn't work contact your SIM Provider for a replacement SIM Card or try more troubleshooting methods.

SIM card. Do you have a SIM card in your phone? If you don’t like me you will see an sos next to wifi and the battery. If you do, there is probably a problem with it.