Greetings!
Welcome to Microsoft Q&A forum.
The following link shows the max storage for Business Critical 4TB. You may upgrade your database to Hyperscale.
Can I move my existing databases in Azure SQL Database to the Hyperscale service tier?
What is my downtime during migration from an on-premises or virtual machine environment to Hyperscale, and how can I minimize it?
How does the Hyperscale service tier differ from the General Purpose and Business Critical service tiers?
Can I bring my on-premises or IaaS SQL Server license to Hyperscale?
Hyperscale can go upto 128 vCores depending on the region and hardware availability. You may want to explore their region and Hyperscale premium-series in the pricing page.
https://azure.microsoft.com/en-us/pricing/details/azure-sql-database/single/
Thank You!