Ex controls my account

My ex boyfriend used to have his phone under my account. Since we’ve seperated, he’s hacked my account multiple times. I’ve tried everything, calling and telling them the situation, they said they blocked my account from being accessed by anyone else but he still keeps getting into it. I believe it’s because he knows my social security number. He uses it as “leverage” to be able to turn my devices off (including my sick father’s phone) for bills that we still share together (joint accounts with both of our names), thinking I won’t pay when I have never been inconsistent with payments. Is there anyway to keep him from hacking my account? The login is currently his email and whatever password he’s set. Every time I reset it, he just manages to change it again.