Controlled phone through family sharing

I was told by spectrum to take my phone to Best Buy to find out it was hacked and being controlled! I was beginning to think I was going insane until after 3 hrs of looking over my phone , they tell me that my boyfriend at the time was controlling thru family sharing and basically there was nothing I could do because we are on the same network, my question now is,,,,, is this true , is there anything I can do and what if so?