There are plenty of synonyms for the phrase "hanging up on," each with its own subtle connotations. "Disconnecting" implies a less aggressive action, while "breaking a connection" is a more formal way to phrase it. "Terminating the call" is a more neutral option, and "dropping the call" can be used to describe an unintentional disconnection. If you're looking for something with a bit more attitude, "cutting off" or "snapping" work well. "Giving the cold shoulder" or "ignoring" could also be used to describe hanging up on someone in a rude manner. Whatever synonym you choose, be sure to use it appropriately for the situation.