I just copped a $200 off discount through T-MO. I had to upgrade my LGG3 in order to get the discount. So instead of paying $629.99, I walked out the paying only $429.00...not a bad deal if you ask me.
No, my G3 was paid in full, so I kept it...they wanted me to upgrade to the G5 and rewarded me with $200 off...I suppose you would have to pay off the remaining balance or roll whatever balance remains on your EIP into the price of the new G5.