Airtel — network issue in mnp sim

I recently changed my mobile network from bsnl to airtel via mnp. My bsnl sim was cut after 6 days and is showing no service yet there is no network on my airtel sim. On asking the retailer, he said the sim has been activated. I have tried every way possible, called the customer support, they said to wait for 24 hours and it's been 72 hours but there is still no network. Now they're saying to change the sim. What am i supposed to do?