Chosen Solution
Sim is not working and unable to call, send text or use mobile data. It shows a message saying " Failed to update cellular services “.
If you input *#06# into the phones keypad does it bring up your IMEI number? If it doesn’t you will have a board problem. On the iPhone 7 series this is mostly caused by prior repair on the Audio IC where too much heat has been applied and effects the Baseband CPU which is directly underneath.
A web site called iMobie has a page dedicated to the exact problem you’re having, and it’s specifically about your iPhone 7. Take a look through the suggestions and see if one of them helps. How to Fix Cellular Update Failed on iPhone - New Guide Here’s a summary of their ideas; see the web page for details on each item. Update your iPhone iOSTake Out the SIM Card and Put it Back inActivate and Then Disable the Airplane ModeSwitch the Cellular Data On and OffDisable the WiFi Calling and Voice LTE OptionsSearch for the Latest Carrier Settings Update Their last step suggests downloading their software, but personally I’d hold off on that; rather let us know if any of the above items helps and if not come back and we’ll see what else we can do to get your phone working again. The last item on the list looks to me like one of the more promising fixes. Hope this helps.
Try going into settings, general then scroll down to reset. Click on reset network settings and see if that works. You’ll have to re enter any WiFi passwords as these will be removed.
