* Is there an software update for your unit? This can update carrier settings which could resolve the issue.
* Have you attempted to restart the phone to see if service will reconnect?
* Did you add any other APNs, which could interfere with service depending on the provider.
* Ensure you're not in Airplane Mode.
If you attempt to use another sim card and it does not read on your phone there may be an issue with the unit. If the sim reads, then I would contact your carrier to see if the issue is the sim you're currently using or possibly just a service issue with the carrier.
My huawei p7 is out of service and the phone connection been discontented more than a month but when I put a SIM Card it shows SIM card putted and still my phone shows No service.
1 
What did you do prior to the "no service".
* Does your carrier have any issue with your sim?
* Did the unit get wet?
* Was it dropped?
* Update any of the software/firmware?
* Is there an software update for your unit? This can update carrier settings which could resolve the issue.
* Have you attempted to restart the phone to see if service will reconnect?
* Did you add any other APNs, which could interfere with service depending on the provider.
* Ensure you're not in Airplane Mode.
If you attempt to use another sim card and it does not read on your phone there may be an issue with the unit. If the sim reads, then I would contact your carrier to see if the issue is the sim you're currently using or possibly just a service issue with the carrier.
Hope this helps.
由 Juax 完成的