Mahanagar Gas — I have been Charged a wrong bill BP No- [protected]

I have been charged a bill pf INR 25817/-
Your executive says that there was a leakage which has caused this. We have disputed this amount as we have no records of this much amount being used. We have raised multiple complaints without any resolution.
No person visited or repaired a leakage. Only one person came and asked for bill payment in cash which we denied and paid online. After that he started threatening us.
Now we are receiving disconnection notices.
If this complaint is not resolved we will have no choice but to follow up with consumer forum.
This is absolutely wrong