Got problem with bill

[Manjit3]

From this month my bills is going high but I am in contract. And I don't want to pay extra 

[PandJ2020]

Once bills are generated they need to be paid (otherwise issues can occur including late payment charges and reporting to credit agencies where applicable)

Have you looked at your itemised bill to identify the changes?  Billing is monthly in advance so the end of a minimum term can be charged earlier than expected.