Tips for these tantrums PLEASE!

Hello mamas!

My 20m old is really throwing tantrums when he doesn’t get his way. I mean falling back on the floor and screaming and even hitting. I’m pretty sure that the hitting the was something learned at preschool because it didn’t start until he started school. Anyway, me and my husband have absolutely no problem taking something that he shouldn’t have and explaining why he can’t have it and trying to replace it with something else and distract him. But he will get so mad that he throw stuff and scream and swat his arms and hit. And that is just not ok. At home we just ignore it and continue on until he eventually realizes that no one is paying attention and he just stops. But today we went to church with my family and he wanted my husbands phone which we said no we don’t play with daddy’s phone but you can color with this coloring book and crayons. He literally went limp and fell on the floor under the pew mad and hitting at us. My husband took him out. It was not pleasant. Another example is him knowing what no means and continuing to do it anyway and then getting mad and throwing a tantrum when one of us stops him. I’m just at a loss of what to do. Is this just a phase like people keep telling me or is there something we as parents can do?