Airtel — invalid internet charges

I activated internet roaming package through my airtel app before going to colombo and as per package, i was given 3gb free internet. After my visit from colombo, it is informed to me that i have used more than 3gb of internet. During my visit in colombo, no single message came from airtel that i have almost used 3gb net or exhausted my 3gb free usage. Further, in the airtel app also, no where it is mentioned that i have to myself monitor 3gb.
Without any intimation from airtel and nothing menioned in terms and conditions about self monitoring, my charges are invalid and not acceptable.