Sim locked but t mobile says fully unlocked

Sounds like reseller flex policy device.  The device is not in T-Mobile’s system as they did not sell the device.  It was purchased from a third party which will lock itself to the first sim put into it.  BestBuy, Walmart, and Amazon for example of 3rd party vendors.  You will need your receipt(with IMEI) AND you need to talk to elevated T-Mobile support for them to put the device into the system to unlock it.  It will take time because they do have to verify with Apple to make sure everything checks out.

if youre experiencing this as well keep in mind that even though you purchased it the device must be on the TMO network for a certain amount of days before it can be unlocked..along with a few other criteria that must be met in order to have it unlocked.

for exampl.e...are you a TMO customer? did you purchase the phone from TMO or through some other route? was the phone ever on TMOs network? and for how long?

Device eligibility is determined as follows:

• The device must be sold by T-Mobile.
• The device must not be reported as lost, stolen or blocked.
• The account associated with the device must be in good standing.
• The device must also satisfy all the Postpaid or Prepaid unlocking requirements outlined below.

Unlock eligibility for mobile devices on Postpaid plans

• The device must have been active on the T‑Mobile network for at least 40 days on the requesting line.
• If the device was financed or leased through T‑Mobile then all payments must be satisfied and the device must be paid in full.
• If the device is associated with a canceled account, then the account balance must be zero.
• T‑Mobile may request proof of purchase or additional information in its discretion and certain other exceptions may apply.

Unlock eligibility for mobile devices on Prepaid plans

• At least  365 days  must have passed since the device was activated on the T Mobile network.
• If the device was activated less than 365 days ago, then the   Prepaid account associated with the device must have had more than $100 in refills during that period for each line active on the account.  In   addition, more than 14 days must have passed since the device was purchased.
• No more than 2 mobile device unlocks have been complete per line of service in the last 12 months.
• T‑Mobile may request proof of purchase or additional information in its discretion and certain other exceptions may apply.

if all of the criteria has not been met for either Post paid or Prepaid then they will not unlock it.

also adding on..if you are not the original purchaser then they will need to be the one to contact TMO..not however ended up with it after the fact.