There are multiple ways to block your Vodafone SIM, which you can find below:

Via Online:

• Open Vi Sim Website Here – Click Here
• Scroll down to bottom and click on Block SIM Online. or Directly you can go here
• In Next page enter your Vi mobile number and then click on get otp to block sim.
• Now enter the 4 digit OTP where you received in your alternative mobile number and email id.
• Then Click Conform to block the sim.

Via store:

Another option is to walk into a nearby Vodafone showroom or store and request the executive to block your sim card. The executive will ask you to fill out the necessary paperwork and verify your number, and then your number will be blocked.