Hello there, tacarra12.
The following link from the online iOS8 iPhone User Guide goes over how to drop a person on a conference call:
Conference calls - iPhone
http://help.apple.com/iphone/8/#/iph3c99551d
With GSM, you can set up a conference call with up to five people (depending on your carrier).
Note: Conference calls may not be available if your call is using VoLTE (Voice over LTE).
Create a conference call. While on a call, tap Add Call, make another call, then tap Merge Calls. Repeat to add more people to the conference.
Drop one person: Tap
next to a person, then tap End.
Talk privately with one person: Tap
, then tap Private next to the person. Tap Merge Calls to resume the conference.
Add an incoming caller: Tap Hold Call + Answer, then tap Merge Calls.
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.