BSNL Roaming Woes: Stuck on 2G/E in AP with Bihar/Jharkhand SIM - Need Help!

My bihar, Jharkhand state bsnl sim is only giving E signal/2G and most of the time tower disappears. Facing this issue from 2 days , tried several restarts and sim reinserting . currently living in Andhra Pradesh and my friend's bsnl which he get from Andhra Pradesh itself works fine , while I am not getting 4G these days even in outdoors.