Hi @Devesh_Chauhan , my name is Andrew, from the Moz Customer Support team. I've modified your plan to the Moz Pro Standard plan as you wanted. This has attempted to charge you a pro-rated amount immediately, but some authentication is required by your bank to ensure this charge goes through. I believe you will have received an email about this, if not please contact your bank and ask them about 3D Secure. Once that authentication is complete, the charge will go through and you'll be on the Moz Pro Standard subscription as requested.
Please reach out to help@moz.com if you have any issues at all!