Apparently once a week isn't enough

Narcissists suck.

goodbye mother, hello therapist

Once a week? Are you too busy to call her every day, Mr. Fancy Pants?

Okay so unless she actually has a normal conversation when you call, just don't anymore. There's no use in putting emotional effort into something if all you get in return is abuse over not putting in even more, that's ridiculous.

Stop.

Does she have a favorite tv show? Call her during that, every time.

Don't call her for two weeks. Then if you hear one word of abuse, interrupt and mention that you're not calling back for two more weeks if she continues. Hang up on her if she does, and follow through. Accept calls from her but hang up immediately if she abuses you, and reset the two week clock. Only violate this rule in an emergency, and you define the emergency, not her. Either she catches on and won't abuse you anymore, or she earns her loneliness. This isn't ok, OP.

Then don't call her anymore, OP. Don't want to make a liar out of her, do we? ;-) Good luck dealing with her, OP!

Howard! Why don't you call more often? Ever since you moved in with your floozy, you've forgotten about your poor mother!