Dear @Reddy, Manjunatha (SP),
Thank you for posting your question in the Microsoft Q&A forum.
Based on your description, you wonder how can block Sunday availability in Microsoft Bookings.
Are you using Personal Booking or a Business (shared) booking page?
In case you're using Business booking page, here is suggestion you can try:
Block Sundays using Business Hours
Open your Bookings calendar
Select Business information
Choose Business hours
Set Sunday to day off
Save
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