I too am a T-Mobile customer. On Sunday and Monday the 6th and 7th of this month in two separate incidences my SIM number was also changed. I don't and have n

I too am a T-Mobile customer. On Sunday and Monday the 6th and 7th of this month in two separate incidences my SIM number was also changed. I don't and have never had an Instagram account. In the first instance I received a notice that someone using my phone logged into a Yahoo account I once setup for a test but never really used. During the second instance I received an email with a Google verification number. I guess that time I got the SIM changed back before anything could really happen. So far there have been no ramifications in either case. No passwords were changed (although I changed a bunch after that) and I've seen no other effects. I've requested that T-Mobile look into the issue but have heard nothing back yet and I have not checked back with them.