Airtel — validity of sim and outgoing disabled

Iam using airtel prepaid sim for the past more than 10 years. Earlier i got a message that my sim validity is upto 2030. But all of a sudden my out going calls disabled though i have rs.157 balance. A message received to recharge for enabling outgoing calls but didn't mentioned how much to recharge. This is not fair on part of the service provider inconveniencing the long lasting customer.