Another person using your account would need to have accessed your account using the platform you selected for the social login. Because of this, your first step is to regain control of the account you use for logging in first. Then change the password and add any additional security measures (such as two-factor authentication) to the account to protect it. This will give your Threshold account back and will also lock out the person who had accessed it if your social account platform forces devices to log in again after a password change.In other words, if you use Apple for your Threshold app login and you suspect that someone is using your Threshold account, this is because they have access to your Apple account. Your first step would be to gain control of your Apple account again and that would restore access to your Threshold account.