Hi Mahesh,
You should receive a Thank You email within 5 business days after the training ended. Has it been that long in your case? Please see post below:
Microsoft Virtual Training Day (MVTD) event
If after 5 business days you attempt to schedule the SC-900 exam and it doesn't show your discount on the discounts page, please ask a question in the Microsoft Credentials forum. They have support moderators over there that can help you.
Please click Accept Answer if above was helpful.
Thanks.
-TP