Twitter – How to remove the phone number from someone else’s Twitter account

I got a new phone number, and I am receiving dozens of Twitter notifications an hour even throughout the night.

From everything I've seen texting STOP to the Twitter short code, which to my understanding is 40404 (that's the number the notifications are coming from) should remove my number from the old user's account.

Unfortunately, this is not working. It is a prepaid phone, the notifications are burning through all my minutes, it is keeping me awake and distracted and I need it to stop.

I have tried adding the number to my own Twitter account, but it is blocked because someone else has it on their account.

One reason I could think of that it may not be removing with the text to the short code is that the offending account actually has a Google Voice number listed as their mobile number which is forwarding to me. (Yes, I understand this does not make sense with the previously mentioned not being able to add it to my Twitter account, but I'm desperate.) So I tried adding the number to my Google Voice account, but that did not work either.

I can't think of anything else to do. Please help.

Followup: I just tried tweeting myself from their phone so that I could find out who it was and ask them to remove the number from their account, but it seems the tweet never went through. Maybe the account was deactivated?

Apparently you can search Twitter users by phone number. I tried searching by phone number and this person seems to have disabled that.

Since I'm getting no response at all from 40404 (including tweets, STOP, HELP, START, etc) I thought I'd try their international long code (+44 7624 801423). It did not work. I then checked with my carrier, and they do not support international texting. However if you are reading this for help, and your carrier does, please note that I read Twitter requires U.S. users to use the short code, so it probably will not work anyway.