Ex boyfriends

I'm in a relationship with a new person called Sam and my ex boyfriend used to bully me all the time make me feel low , we haven't spoken for a while now but the other night he texted me we was just speaking not flirting just generally speaking to eachother I didn't want to be rude so I kept on replying but now he's turnt all horrible again after he found out I have a new boyfriend other than block he's number what can I do? I've blocked he's number in the past but he just found a way to ring and text me of other people's phones ?