Why are other people's searches showing up on my YouTube?

[AC Question]

YouTube searches that are not my own are showing up in my search history. Calendar updates that are not my own are showing up as well. I work at a cell phone repair center, and I think my Google acocunt is linked to other phones. I changed my Google password, but it hasn't stopped this activity. What should I do?

 

[pkcable]

Welcome to Android Central! Are you signing on to any of the phone's you repair, or any of the demo phone's at your shop? Perhaps people have done the searches on those phone's while your account was still signed on?