So back in febuary I went from ATT to T-Mobile. With a galaxy s4 ATT provided me an unlock pin popped in my tmobile sim and it was unlocked. Later I had to send in my phone because my camera was malfunctioning.. I asked the rep before sending in my device if I will lose my unlock.. They said no. They repaired the phone.. Replaced the camera and PBA (motherboard) because it was also power cycling. So when I got the phone back I popped in my T-Mobile Sim and it was asking me to enter in the unlock pin.. Luckily I had the same unlock pin from febuary I entered that in and nothing happened I tried it again nothing. so I called Samsung and they said I need to call att and request a new unlock.. Called att requested a new unlock and they provided me with the same unlock pin like the first time. and they said only one unlock pin can be assigned to one IMEI number. called Samsung back and said they can't do anything which is B.S... just paid for this phone.. anyways now my phone is acting up again.. Running slow.. Some of the apps show "unavailable" or not responding. I went to the service menu by doing the *#0011# to try doing an unlock another way but it won't work for me.. one thing I caught was the IMEI CERTI: NA.. Idk if tht has something to do with it? any one have any tips? Or that can help?