The software of my a53 has been changed by a third party before being sold.

[Khan1988]

The network of my phone has stopped working completely 

[realaud]

How do you know some third party changed your software and what does that have to do with your network connectivity? Please explain your issue in more detail.

[Khan1988]

When I did a phone diagnosis, that's the feedback I got. So I checked if the phone has been rooted. And YES, the phone was rooted . They changed the phone's RAM and ROM from 6/128 to 8/256. So I unrooted the phone and the memory changed back to the normal one that comes with the phone. so after unrooting the phone, the network link just went off. when I try making calls, the feedback I get is 'not registered on this network' . I contacted sumsung customer care and explained everything to them. I was taken through various troubleshooting, but none worked. I ended up resetting my phone to the factory reset, and it didn't solve the problem

[realaud]

I'm actually surprised that Samsung service was willing to help you with a rooted/unrooted device, even though you weren't the one who did the rooting. Was the network ever working and stopped working after you unrooted the phone?  Is it your phone network not working or your wi-fi (or both)?  If you are near a uBreakiFix location, perhaps they can flash new firmware for you.  Otherwise, I'm sorry, you have a doorstop.  If this was a recent purchase, contact the vendor who sold it to you and explain that they did not sell you a properly working device.  They may not give you a return option, but at least they will be aware you know they are shady.

[Khan1988]

The wi-fi works fine. The internet and phone calls were working fine until I unrooted the phone. Now, only the internet networt and call network are not working now. I've contacted the vendor. She made me send her some screenshots. I'm now waiting for feedback from her.

[Khan1988]

I'm so frustrated right now. Bought the phone 2 weeks ago

[realaud]

Unfortunately, these are the risks of buying used devices from uncertified sources. Doesn't help you now, but always make sure you know if there's a return policy or if you are buying "as is". You said you contacted Samsung support, did you contact your carrier?