T-Mobile Unable to Unlock Phone?!?

So, I'm leaving T-Mobile after several years.  My employer is paying for a family plan w/ another provider as a benefit - So nothing T-Mobile did, you just can't beat free :)  I never switched as I never had a problem with them and I've been a fan, but the past week is starting to change that.

As part of moving, I had a balance on a device which I paid off, and the following day (after seeing it was eligible) contacted T-Mobile to have the phone unlocked.  I was told it takes 24-72 hours, and it would be unlocked by Saturday. 

Saturday came along and the device was locked.  I went into a T-Mobile store, who told me I'd have to call for the unlock, but advised me to keep the account open until I had the phone unlocked.  That evening I chatted with T-Mobile via 611.  I was told it takes 24-48 hours, and was assured it would be unlocked by Monday. 

Yesterday, the phone was still locked.  I called T-Mobile, and was told it takes 24-72 hours.  I asked to be sent to a supervisor, who started telling me how she could understand my frustration… Then hung up on me.

On each of these calls I was told I met all eligibility to have the phone unlocked, but when they tried to do it there was "an error".  In the meantime, I have to keep this plan open costing me $40 a week.  I feel like my phone is being held hostage.

Is there a secret to getting T-Mobile to give me my paid-for phone?  Again, my account is fully up to date with payments, the phone is paid off, and I've had it for over 9 months (well over the 90 days for eligibility).