I need advice on how to handle a service provider

I applied for an Airtel sim on the 20th and gave the port in details for it to be processed. I got a number of calls when they had to sell the sim card but the one I received isn't working. I've been asking them to help me since the 29th the date it should have been activated. Instead of giving a solution they have only delayed the process and not been answering my calls or messages. I'm so fedup with their lack of service. If they can't activate the service at least give me a port out code so I can take another provider. They have left me stranded and switched off all contact numbers. I don't know what to do. Please help me.