Fixed cmdlet description

Fixed cmdlet description from Get- to Set-

Author: get-itips

exchange/exchange-ps/exchange/client-access/set-CASMailboxPlan.md

@@ -11,7 +11,7 @@ monikerRange: "exchonline-ps"
 ## SYNOPSIS
 This cmdlet is available only in the cloud-based service.
 
-Use the Get-CASMailboxPlan cmdlet to view Client Access services (CAS) mailbox plans in cloud-based organizations.
+Use the Set-CASMailboxPlan cmdlet to modify Client Access services (CAS) mailbox plans in cloud-based organizations.
 
 For information about the parameter sets in the Syntax section below, see Exchange cmdlet syntax (https://technet.microsoft.com/library/bb123552.aspx).