Hello Adetoyosi Elegbede,
Thank you for posting this in the Microsoft Q&A Community.
From my understanding, you are not able to create an Azure App Service due to an error that says you are not allowed to create or update the serverfarm within your subscription.
Please be informed that this is a known issue and is currently being reviewed. However, kindly check this thread which lists related issues and how they have been resolved.
Babafemi