@Salim Thank you for contacting us!
Regarding VM size/core availability, there could be two reasons:
- There could be region availability constraints
- There could be limitations/resource constraints region or at subscription level
For the first one, you need to choose a different region as a workaround
For the second one, you need to contact Azure subscription management team by raising a support request to enable region/resource availability for your subscription.
Here is the link - https://learn.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request to create support case. The ticket enables you to work closely with the support engineers and get a quick resolution to your issue.
FYI: Azure billing and subscription management support is provided free of cost!
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Am sorry to say, in order to increase quotas or limits you must upgrade your Azure free account to a pay-as-you-go subscription. Reference link - https://azure.microsoft.com/en-in/offers/ms-azr-0044p/