Yes; standard practice is to use the [Obsolete] attribute for obsolescence in .NET.
EDIT:
Keep in mind that this will not formally apply to the WSDL / service, as shown to the consumer. Because WS is the standard for all technologies; protocol must be followed. With this in mind, your goal of distributing changes to the consumer, unfortunately, will be related to the release of notes, as indicated in this question . Although not perfect, it provides a vehicle for obsolescence.
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