Airtel — Wrong Billing Airtel

I gave this Nokia 105 mobile to my mother who is close to 55 years old. she knows only how to answer the calls..but i see there is number 5924102 getting dialed everytime..and this number charges 5Rs per minute which is very too much.. She doesn't even know how to operate how can she dail the number for more than 1:40 minutes

Why Airtel is not blocking such numbers. I have seen these numbers begin reported by several people.