We recently got the SLT Plus facility at our office and I was wondering how to use the Conferencing and Call Waiting features, googling (as is usual on any Sri Lankan related search) did not return any result so I had to resort to calling SLT and this is what they had to say on how to use each feature.

Conference Call
1. Make your first call.
2. Tap the cradle button (cut the line).
3. Make the second call
4. Again, tap the cradle button.
5. Press number 3 to connect all three lines.

Call Waiting
1. While you’re on a call if you hear beeps this means you have a call waiting.
2. Press 2 to switch to the second call.
3. Press 1 to switch to the first call.