On your Amazon Alexa App go to Skills and search for Cosy.  When Enabled you will find the Skill in "Your Skills"

Yes, to be able to get Cosy and Alexa working together there are a couple of things you need to check first: - You have a working Cosy system - Your Co...

Once you have added the Cosy skill to your Alexa account, you'll need to link your Cosy system so that Alexa can control it. To do this, simply clic...

After Alexa is connected to your Cosy account, you’re ready to try out some of the commands. Here are some examples of what you can ask Cosy to do: ...

Yes, go to your skills page and select Cosy.  In here you will find the 'disable skill' button.