Hi @Vishal Saxena ,
as far as I know it's possible to by an Azure saving plan in a PAYG Azure Subscription.
You can check this in the Azure portal if you try to buy/add a saving plan by selecting the Subscription without clicking on Review & buy
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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten