Hello, teachers, please check if the following sentence is correct:


This contract cannot be canceled effective prior to the expiration of 24 months of its commencement date.

Background:
It is a five-year service contract. To ensure the customer sticks with the service provider, the contract does not allow the customer to unilaterally terminate the contract until a certain period of time. But I don't feel quite comfortable with the word 'effective' over there. Can it just be eliminated?