When I was on 4.3 - My data dropped out and took around 10-20mins to show up again, I just put it down to my network being silly, since I've been on 4.4.2 not had any data/signal issues.
EDIT Same phone as your's, BTU Unbranded.
// LG G3 (D855) // Stock // Stock //
// HTC One (M8) // GPE Stock // Stock GPE//
// Nexus 7 (flo) // Android L // Stock//
S3(White) > M7(Red) > Note 3(Black) > Nexus 5(Black) > M8(Gunmetal)/LG G3 (Titan Grey)