Airtel — bill more than credit limit

I have done int roaming in airtel postpaid only after taken my sim for 5days... After coming from abroad i got a bill of appx 140000 which is jus unimaginable... If a credit limit is set then how could they can give such a huge limit to any of his customers and that also just after 5 days of new sim... Even after having a int roaming pack i got such a shocking bill... This airtel are jus cheating their customers... Jus beaware of this