Is T-mobile iPhone 6 unlocked I bought an iPhone 6 T-mobile from Apple store. I tried my SIM from Sweden and it worked. However tried with another SIM from Ghana but it didn't work, showing "no service". 

Does that mean the phone is locked or something else is wrong?
The "no service" can have other reasons than the SIM card and iPhone lock.

Since it worked in Sweden (with non T-Mobile SIM) then the iPhone is unlocked.

Try another provider or better try a prepay SIM to see if that works in Ghana.