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I'm curious how you determined this. Anyway, since that is an Android phone (the Casio G’zOne Commando, I had to look it up), I think the most likely thing is your ex has your password for your Google account which would allow his to access almost everything remotely. I suggest that you immediately change your password and enable 2-factor authentication, which requires a second source of confirmation (typically a text message to your phone number) before your Google account can be logged onto from any device that you haven’t listed as trusted. It should only take you a few minutes. I’m not certain about the facebook access, but if I was guessing, I’d bet you used the same password for Facebook that you did for your Google account. or he found it through your old Gmail messages. HERE is the guide for enabling 2-factor authentication.