Hello Alpesh
Thanks very much for bringing this question to us, and also for your patience while determining the appropriate answer.
A case is required with our Customer Service team for this type of cancellation. You may submit the case at the following link:
https://customerservice.cloudapps.cisco.com/
You can then search for "service contract termination" and you should find results for different case types. Choose the appropriate option based on your circumstances by clicking "Open a case" on the right-hand side. Once you open the case a member of our Customer Service team will be in touch.
Please let me know if you have any additional questions!
Max Swift