I realize that this is an old topic but hopefully my experience will help someone who comes across this. When you request T-Mobile to port in your MJ number you need to give them your account name and password. Your account name is the number that you are trying to port in. The password is the password that you use to log into the MJ site. The person who was assisting me from T-Mobile told me that the entry field on whatever form they were trying to complete would not allow them to enter letters. Make sure you tell them that you are porting a landline number. Unfortunately most of the reps from T-Mobile are non-native English speakers so listen carefully and speak slowly and clearly. It would also be useful to give them your billing address and zip code since MJ will ask them for it when they receive the porting out request. I did ask MJ via their online chat what the password was since apparently the T-Mobile folks couldn't quite get it right and was told that the password is the password that you log into the site with. If T-Mobile does everything correctly this will result in an email from MJ stating that they are sorry to lose you and attempting to charge $30. DO NOT PAY THIS!!! Click the link, log in, and then just close your browser. I am not sure that this step is necessary but it won't hurt either. I would also ensure that you do not have a credit card on file with them either, take a moment to disable autopay and remove cards on file. It is not necessary to pay for this and it will go through in about a day. It took me about 4 days and numerous calls with T-Mobile to accomplish this but it did work once they managed to enter the password correctly. You may end up dealing with a support specialist but persevere, it will work. Once you get the email from MJ you should be set, look for the text message on whatever phone you put the sim in that your number has been successfully ported.