Reliance Jio Infocomm — billed even after no postpaid services were chosen

Address:

Kolkata, West Bengal, 700075

I have been receiving a bill of Rs. 52on a jio number [protected] which was never used after the free offer ended over a year ago. I also havent selected any postpaid sevice for the number nor any plan. I used jio sims when they were offering 6 months of preliminary service and we were told by the executives that after that tenure we will have to select jio prepaid or postpaid services.But after the free offer got over, I received a message that all my jio numbers have been converted to postpaid without my knowledge. They also asked me to choose a plan. I then converted 3 of the sims to prepaid and are still using it. But suddenly I get emails from jio about this number and I am surprised as I have neither selected the type of service nor any postpaid plan.So how am I getting this bill?