[Q] I messed up *#*#4636#*#* settings HTC One E8 topic

Guys,
I guess I've messed up some settings in *#*#4636#*#* (Testing Menu) in the
Phone Info-> Select Radio Band -> Set GSM/UMTS band.

I'm running Reliance CDMA in Slot 1 and Airtel GSM in Slot 2.

The phone doesn't recognize Airtel SIM in Slot 2 anymore.
I tried inserting the Airtel SIM in Slot 1, but even then it didn't work.
Restarted also didn't work.
Called up Airtel customer care to check, but my number is very well active.
I need to try other nano-SIM in Slot 2 and give it a try.
Will update with my findings here tomorrow.
Any inputs really appreciated.

Thanks!