Hey there andria gvenetadze
Thats a good question and thanks for using QandA platform
I guess Yes, you can upgrade your Azure Service Bus plan from Basic to Standard without deleting the existing service bus.
Go to Azure portal (https://portal.azure.com).
Locate and select the Service Bus resource that you want to upgrade.
In the left-hand menu, scroll down to the Settings section and click on "Pricing tier".
In the Pricing tier blade, you'll see the current pricing tier (Basic) and an option to change it. Click on "Change tier".
In the Change pricing tier blade, select the Standard plan option.
Review any changes to pricing or features associated with the Standard plan. Once you're satisfied, click on the "Select" button.
Confirm and that's it you are done
If this helps kindly accept the answer thanks much.