Bad to hear that there are no bars on network icon on your device. But don't worry i have best quick fix for this issue. Hope this may help you:
Go to Settings > mobile + SIM, tap on Highest connection speed and switch it to 2Gnce you've switched you...
Very Sad to hear about your issue. But i have an idea with which you can downgrade your device's firmaware. But this is ver long process of approx 40 steps. So i don't share all steps but i will share the main steps of this procedure and you can see ...
