[HELP] IMEI unknown. topic

I have spent the past week looking through Google, rooting my phone, learning about Odin and EFS Professional. Everything I've done so far hasn't been much help. My friend got a free Samsung Galax S4 LTE from his other friend, but he didn't need it, so he gave it to me. Everything about it works great. Connecting to my router, adding music and videos... all except one thing, which is the IMEI number; it says Unknown, and I've ran out of ideas how to fix it. I did download some other 1.4GB file and used Odin3 to "PDA" it, but I'm not sure what that even did. I've checked YouTube for suggestions. Mostly it just says to dial some numbers (like #*06#) but when I hit dial after that, I just get a "mobile network not available". I need help from a forum that seems educated on this matter. What do I do? I imagine I'll have to install something, but I can't seem to find out which one. I would really appreciate some help. I need the IMEI number to activate my service for this phone. These are the specs:

Model #: SCH-I545
ANDRIOD VERSION: 4.4.2
BASEBAND VERSION: I545VRUFNC5
KERNAL: 3.4.0 dpi@SWDD5015 #1
BUILD NO: KOT49H.I545VRUFNC5
Hardware: I545.00