September 8th, 2013, 10:51 PM
Join Date: Feb 2011
Location: East Orange, NJ
Device(s): Samsung Galaxy S® 4 vMJA Rooted,
HTC EVO Design 4G™
v4.0.3 Bootloader Unlocked & Rooted
Thanked 195 Times in 168 Posts
You kind of answered your own question. By clicking "Merge", you're using up your +1. Pressing End should only end Line 2 and you can switch back to Line 1. You can then attempt to Add Call again. I will admit I haven't done conference on the S4 yet, so get someone with patience to attempt this with, lol. But there is always a way to "hang up" on Line 2 without disconnecting Line 1 (if your mobile carrier's technology allows it).
Samsung Galaxy S® 4 MJA Rooted with CF Auto-Root Tutorial
HTC EVO Design 4G™ v4.0.3 Bootloader Unlocked & Rooted with HTC SuperTool v3
If it ain't broke, use a sledge hammer.