This is what I did after I changed sim cards
1. dial *5005*7672*00#
2. select "carrier select"
3. choose the original carrier where your phone is locked.
4. tapos choose mo kung saan na uunlock ang iphone mo eg. gsm mode, cdma mode, 6/6p mode. (For me it's 6/6p mode but my iphone is 5C locked to...