Mahanagar Gas — invalid extra charges given in bill by gas station

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My bp no. Is [protected]. The bill of dec'17 was paid on[protected] before the due date. Yet after paying the complete bill the extra charges are added to bill of feb'18, extra rs.1118 including the due fine is added to bill of feb'18. I assume such a mistake are pretty much humiliating for "mahanagar gas limited".
I there by request the concerned authorities to look after the matter and necessary action as soon as possible.
I am waiting for your reply.