Open new PowerShell window, you may use cloud shell on Azure portal as well by clicking the cloud shell button at the top right at your portal screen.

Copy and paste the following PowerShell code and execute it - it will create a function for the current PowerShell session
function Cancel-AzSQLImportExportOperation
{
param
(
[parameter(Mandatory=$true)][string]$ResourceGroupName
,[parameter(Mandatory=$true)][string]$ServerName
,[parameter(Mandatory=$true)][string]$DatabaseName
)
$Operation = Get-AzSqlDatabaseActivity -ResourceGroupName $ResourceGroupName -ServerName $ServerName -DatabaseName $DatabaseName | Where-Object {($_.Operation -like "Export*" -or $_.Operation -like "Import*") -and $_.State -eq "InProgress"}
if(-not [string]::IsNullOrEmpty($Operation))
{
do
{
Write-Host -ForegroundColor Cyan ("Operation " + $Operation.Operation + " with OperationID: " + $Operation.OperationId + " is now " + $Operation.State)
$UserInput = Read-Host -Prompt "Should I cancel this operation? (Y/N)"
} while($UserInput -ne "Y" -and $UserInput -ne "N")
if($UserInput -eq "Y")
{
"Canceling operation"
Stop-AzSqlDatabaseActivity -ResourceGroupName $ResourceGroupName -ServerName $ServerName -DatabaseName $DatabaseName -OperationId $Operation.OperationId
}
else
{"Exiting without cenceling the operation"}
}
else
{
"No import or export operation is now running"
}
}
Cancel-AzSQLImportExportOperation
use the function
Cancel-AzSQLImportExportOperation
to cancel an Import or Export operation you need to provide the Resource Group name, Server name and Database name where the operation is currently running.