I tried to transfer from ATT to another server since April 20 and today is May 12. No one could help me and I got a lot of passing the buck and people who said they were working on it who days later did nothing. I have told my story to so many people, in fact three just today, that I am so glad this dilemma is over.
Here is the scenario: I was given an unlock code. When that was put in it did not work it immediately said too many attempts it needed the MCK Code. What no one realized in all the people that I spoke to over the last four weeks or more is that you need both codes when the phone becomes permanently locked. You put in the MCK code, then the unlock code on the next screen (read the prompts and what it is asking you for). That fixed the problem 1, 2, 3. Now at the beginning you will get a port pin to give to the new carrier to port over the phone number. There seems to be two parts to this unlock the phone thing. At one point I was told the phone was unlocked, gave the port pin to the carrier and my number went over, but the phone indicated it had no service and was still locked to ATT. Also if you have an apple phone tell them to do an e-sim, which they can do over the phone, and once you turn off the phone and turn it back on, you are on the new server. If not, you can go to the store, they will have to use a physical sim, if the previous method does not work for iphones only.
Just wanted to let you know what I went through the past few weeks, and I would not wish it on my worse enemy. I see a lot of stories about the MCK Code, I hope if you get into this dilemma, this will work for you as no one else took the time to do their research and find the solution, which only took just a few minutes. Sorry this not a question, but this should be posted to the forum, which I thought this was. Please share this with other workers as they need to know this, or just do their research because things change often.