Thanks very much! I did call your customer support number and a very nice, patient young lady walked me through the settings on my cell phne to turn off the notification. (I had to turn off notificatiion in order to turn off the callback, but I now know how to see balance and expiration date any time I want, displayed in a concise format, so I'm happy.)
NOTE: I tried to click "accept solution" below your reply, but it didn't work - some inconsistency between the forum and my browser.