Why my phone says "No Service", even the sim card is properly inserted?

[AC Question]

I have a HUAWEI G7+ purchased about 2 months ago and recently above issue was noticed. I double checked the sim card with another device and it works properly. I checked the phone with another working sim card and also i tried both sim ports with my regular sim and another working sim. but the results were same, "No Service". I have a good signal strength in the area i live.
Can anyone help me sort this out?.
Thanks.