Can't receive or make calls. Can do everything else (SMS, WiFi,etc.)

Hi, I accidentally dropped my phone on my bed with no damage on the outside nor on the screen (I have a protective case). The sim card icon appeared (which meant it was dislodged inside) and I just turned off and reinserted it and it got detected again.

Unfortunately it seems like the phone can’t receive or make phone calls at all.

I have cellular signal, can do SMS perfectly fine, can do mobile data at 4G/3G, have WiFi, and bluetooth and everything else.

The only thing that doesn’t work is the phone calls. I can hear the network operator but it doesn’t proceed with the call at all (even calling my own house).

Things I’ve already done:

1. Powered down the device, reinserted the sim. No luck
2. Tried calling from other phones to my phone. Even used my landline. No luck.
3. Reset settings on WiFi, mobile data, etc. No luck.

Could this be an adapter problem? Hopefully not. I’m still within warranty and I’m not sure if this covers it.

I tried using sim card 2nd slot, calls now worked for some reason. What could this mean for my phone?