How do I update the carrier list for Photo to Phone?

How do I update the carrier list for Photo to Phone?

Warning
Discontinued Option
The carrier selection option is no longer supported by Darkroom Software as most carriers now block this method of sending SMS messages
Darkroom Phone is now included with a current maintenance and is recommended for most users.
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When using the Photo to Phone feature without Twillio you can send images through the email system. That will prompt the user for their phone number and their phone carrier. This list of carriers are setup for general use in the U.S. but it can be edited to add or remove carriers in your area.
Go to C:\Program Files (x86)\Darkroom Software\Darkroom Booth\MobileCarriers on your computer's hard drive. Open the file CarrierList.txt in notepad or other text editor.
The carriers are listed one on each line with the Display name, the email extension they use and the file name of their logo. Like this
AT&T, @mms.att.net, ATT.jpg
The logos need to be in .bmp or .jpg format and no larger than 200x200 pixels.