if they said it was a clutch issue and you asked them to change it, it's not your fault that they misdiagnosed what was wrong. They are professional tradesmen, you didn't ask them to guess and just swap good working parts for new ones. They have fitted unnecessary parts and charged you. Have they even changed them? Did they save the old parts?
If you get advice over a forum (someone that can't see/hear/touch your car) and you swap parts yourself, you can accept someones advice might be wrong, but you didn't guess yourself so that you didn't waste time and money.