Thanks for reaching out to the Chromecast Community forum and I'm sorry to hear that you're having an issue with your Chromecast. Let's sort this out.
A few questions: what type of Chromecast with Google TV device do you have, is it the 4K or HD model? How close are the devices to each other? When did the issue start? What's the OS version of your phone? Is it updated?
Give these steps a try: