Phone says sim card is missing after an update

If you get an alert about the SIM card in your iPhone

1. Make sure that you have an active plan with your wireless carrier.
2. Update your iPhone to the latest version of iOS.
3. Restart your iPhone.
4. Check for a carrier settings update. Go to Settings > General > About. ...
5. Remove your SIM card from the SIM card tray and then put the SIM cardback. ...
6. Try using another SIM card.

https://support.apple.com/en-us/HT201420

hi this mr white and i would like the unlocking code for my gt7100 so i can put a differnt simcard cos at the it is on o2 and i want to my lebara sim card in it

You didn't save them to your SIM card on your old phone.
If you take your old phone & your new phone into a store you can ask them to switch the contacts over & they should be able to do it right then in there in just a few minutes.

when your sim card enter there must display of sim card name and there having also network.

Hi, One of the reasons why this message appear is the phone does not accept any other simcard because it is lock to a particular service provider,if you want to use any other sim provider prior to you country,the phone needs to be unlock all network provider,and this may possible by bring the phone to any mobile service shops near you for the unlocking service. Another reason of this case is the improper updating of phone firmware,might luck something on the procedure, we have a technical term distinguishing this type of problem,usually when we flash or update a phone using a gsmgadget and we miss some settings to generate,we encounter this problem. To make everything clear about this matter,better ask assistance to a mobile service center and the will fix this problem. Thank you for visiting FixYa....

This is not a big issue, what you need to do is to just upgrade the OS of your handset, actually your current OS is corrupt either due to some malfunctioning or due to some file you have tried to download from the web. Just simply check the latest OS available and replace it with your current one. I hope your issue will be resolved after doing this.

might be some problem with the slot1..in reading sim

u cannot lock ur phone but u can lock block ur sim card
if ur phone cdma den ok
if not its gone

I have seen where you can reset this by pulling out the sim card, booting up the device without the SIM card and lettign it error out the pulling the battery and replacing the SIM card and battery and letting the OS load.  Who is your carrier?