Airtel — 4g airtel network problem

Address:

600061

I was recently issued a 4g sim card as part of an upgrade by airtel, when i inserted that sim into my phone (Oppo a57), it did not recognize the sim. After speaking with their customer care without any proper support or technical understanding of the problem (Their approach was to "change my phone", i have an oppo! I at the very atleast asked them to revert to my 3g earlier sim since that was working alright, but it seems that is also a problem for them to do. Their customer support is not responding and i am left with no connectivity for quite awhile now.