When I subscirbed to RM38 M Basic plan last year. The Celcom staff said when usage reached 1GB service will terminate and user will need to manualy subscribed to daily plan of RM3 compared to RM5.
Pay per use charge is 10cents/1kilobyte. So 10Mbyte will be RM100. The RM250 is the maximum they charged before the service is disconnected.
Celcom mobile internet, How to know when we reach the quota?