(and ditto to @Yeswecan
) I can't believe that your mother gave out your number like that! For all the negative things about my mom that I put out here on TAM, I will say this: there is no way in hell that my mom would give my phone number to ANYONE save for immediate family. If anyone else is looking for me, she'll take a message, and I might get it eventually, but she is way protective of my privacy. And if my XH called her to try to find me (not that it would happen, I've had the same phone number and email address for over a decade, and they're not changing, like ever), she would lay into him and rip him a new a$$hole before he had a chance to mutter a few sentences. She's not a great parent, but I do have to give her credit where credit is due.
If my mother did what your mom did, I would be calling her up (from a blocked number) and saying, "I had to get a new number because you gave my old number to my crazy XW. Given that you have shown me that I cannot trust you not to distribute my contact information, I will not be giving you my new phone number either, until you have re-earned my trust." Show her there are consequences to her actions.
With the new number, be selective about who you give it to, and give them explicit instructions not to give this new number to ANYONE, NOT EVEN YOUR MOTHER. (You can tell them the story, or not. I would be telling fvcking everyone, but that's just me! You can also just say that "someone" gave out your old number to your crazy XW, and you don't want that happening again, so you are only giving the new number to people you trust to abide by your wishes and not give it out... so if someone asks because they don't have it already, that means you didn't trust them enough to give it.)
Regarding the initial call from the XW, you were quite kind and civil. I think you handled that much better than most other people would. Way to stay strong and logical, because it's obvious that she was testing the waters. If she calls again, you may have to cut her off and tell her there's nothing else to say, and ask her not to contact you again.