如何强制Powershell使用新的Azure订阅

I have two subscription one with old cloud service and other is with new cloud service. I am using Powershell to access my new subscription. I have downloaded latest .publishsettings and set it using Import-AzurePublishSettingsFile. My problem is that I always get the old subscription set and could not figureout how to force powershell to use my new subscription. I have two subscription one with old cloud serv