Hello & Welcome to JustAnswer.
Unfortunately, yes. They tricked you into signing up with them and probably scammed you. If the disk is full, if only it is then you should have been able to fix it easily by yourself. These type of scams are generally known as Tech Support Scams. What you can do now is call the credit card company and initiate a charge back, banks and card providers are already aware of these type of scams so it will not be an issue explaining to them what has happened. And, also you should uninstall the program they have installed on your system (if they have) to prevent any further access to them. Let me know if you have additional questions or if there is anything else i can help you with. And, if i have answered the question satisfactorily, please take a second to rate my service by clicking the star icon on the top of this page. Thanks