I just did this yesterday. I transferred to Mint Mobile. I no longer have a landline, so I decided to switch from Tracfone since I will be using my cell phone more. I kept my same number and when I put in the Mint SIM card, I kept getting a message that the phone was locked. So, I did the Tracfone chat and was able to get a person who sent me the process and codes to unlock the phone. Now, I am getting several messages that my phone number has changed, which it hasn't, and I have to go and re-enter it again in several accounts.
When I was just transferring from one Tracfone to another, I used the Transfer Wizard and it worked well. If you are still using Tracfone, then their support line shold help.