Default [Q] how to unlock a us celluar galaxy s5 (sm-900r4)

I was wondering if anyone out there knows how to unlock a unlock my us cellular galaxy s5 (sm-900r4)? I bought it off ebay thinking it would be easy to unlock but to my surprise it was not...I took it to a local shop (genuis phone repair) that said they could. When they tried they said something not right with the phone..the imei only has 14 digits and it needs to have 15? They said it is a true s5 not a I was wondering if any knows how PLEASE HELP!!!