So I wanted to preorder the LG G5 before it had been release. I currently have 3 lines on my account. One line is not used and was basically added to get my wife a discounted phone when hers broke at the time. Last year I had taken the upgrade from line 3 and added it to my main line. No issues there. It was the Edge program at the time. So fast forward a year later. My coworker mentioned how he traded in his phone to get the new S7. Had paid half his phone off and then they used the phone trade in to cover the rest. So he didn't really pay anything to upgrade. I called about doing the same thing. I was trying to switch the edge contract from line 3 to my main (remember I had swapped upgrades) to which Verizon said wasn't possible. The one option was basically keep the 3rd line and keep paying the payment plan, but then just add a new payment plan to my main line. So I could get the new phone on my main line with the new device payment plan while still paying for the 3rd line. I didn't really want 3 payment plans (wife has one). So I thought of another option.
What if I add a device payment plan to my line which would allow me to get the new G5 and just pay off the remaining balance from the payment plan on the 3rd line and then cancel it. Customer Service lady said that would be fine. So sure I was paying a little more upfront but at least my 3rd line would be gone and I would save $20-30 a month by not having that line. So everything sounded great. Well apparently she took the payment to pay off line 3, but then still associated the new device payment plan to that line, but activating the phone to my main line. So here we are now, I still have 3 lines. My main line still isn't associated with the payment plan and I just paid $300 for nothing essentially. Tried talking with a manager only to be told they can't transfer the contract to my line because it's not eligible for an upgrade until December. At which they can switch the contracts and then cancel the 3rd line. Why the customer service rep didn't inform me of all of this in the first place and proceeded with the transaction with how I believed it was going to work. Super frustrated and beyond irritated at this point. Makes me consider trying out another carrier.
Sorry for the long rant, but figured this would be a good place for it.
Or you could pay the balance G5 and own it and then cancel the third line. Depending on when you signed up for the payment plan that was on the third (missing from your original post) you would have had to pay it in order to cancel the line anyway.
If you have a 0% interest CC, pay the device payment in full with that and make the monthly payments to the CC.