If you've changed the exam medium for your SSC MTS form and there is a fee associated with this change, such as  you mentioned, it's crucial to pay it. The fee is likely for processing the change, and failing to pay it could result in your application being considered incomplete or invalid.

If the payment isn't made, there's a risk that the changes you made (in this case, the exam medium) might not be updated in the system. This could lead to your admit card being issued with the original details you provided before the change, or in the worst case, it could result in your application being rejected altogether.

To ensure that your admit card reflects the correct exam medium and that your application remains valid, it's advisable to pay the required fee. After making the payment, keep a receipt or confirmation of the transaction for your records, as it may be needed for future reference.