Some strange issues @ nagpur we have 3 numbers waiting for upgrade and 2 numbers are having no signals since 3 days
Today morning i just tried to access network in 4g sim. It was not working then i tried to put in basic 2g phone. It started working. I again try to latch on 4g network but failed and signal no more.
After 5 mins. It started working again on the basic phone and smartphone.
I think those who are not getting the signals might be there sim is upgraded but when they insert the sim in smartphone. It generally tries to access the Preferred network of your phone (LTE) and as it tries to access. It blocks you 5 mins for 2G access. So that might be the reason.
I experience with 1 number and it is happening since today morning.
So please try at your end.