Unlock iPhone 5 help
The flowchart on unlocking an iPhone (no matter what model or what carrier) is here. If you're having problems with Customer Support with a specific carrier. List the exact words you used to request the unlock and consider getting them to explain exactly what the issue is.

Hold their feet politely to the fire if they are not supporting you as a customer. You will need to be responsible for being clear with them and listening to exactly what they say so they don't "snow" you with irrelevant information. Once you share with them the exact steps you are undertaking (linked below) they will have no where to hide except to admit if they will or will not unlock the device.

https://support.apple.com/en-us/HT201328