4G Connection not working properly A month or so ago, when I turned Mobile Data on the device did not connect to the Internet. I thought that it is a temporary issue with the carrier but it is still not working.

Details of the issue:


It doesn't display anything on the bar icon (on status bar) which shows the network connectivity.
I could connect to 4G using a workaround. When I disable 4G in connection settings, it successfully connects to 3G. (and shows H+ in the bar icon) When I turn on 4G again it successfully connects to 4G and shows 4G in the bar icon.
In System --&gt; About Phone --&gt; Status  --&gt; Network it shows Mobile Network: Disconnected even though Mobile Data is on.


I tried pulling out and putting in the SIM card, switching SIM slots. I can't try the SIM card with an another phone, or an another SIM card with my phone as I don't have access for either for the time being.

Why is this happening? Is this an issue on carrier end or my phone? (it is still on warranty)

My device is Huawei P Smart+ running Android 8.1 (EMUI 8.2). Thank you!
I took the SIM card to a carrier outlet, and they said that it is a damaged SIM card and replaced it. Thanks @Izzy for the helpful comment! :)