Here's the Rogers guide -page 18 - (PDF/needs Adobe Reader):
http://downloads.rogers.com/homephone/Guide.pdf
To use Three-Way Calling:
1. Dial the FIRST person’s telephone number as you normally would.
2. Once they have answered, ask the FIRST person to hold on the line while you conference someone else into the call.
3. Press and release the hang-up (or Link/Flash) button quickly. You will hear a new dial tone.
4. Dial *71, followed by the SECOND person’s telephone number.
5. Once the SECOND person has answered, press and release the hang-up (or Link/Flash) button quickly. Both the FIRST and SECOND parties should now be on the line with you.
If the SECOND person does not answer:
Quickly press and release the hang-up (or Link/Flash) button twice to return to the FIRST person.
If you want to end the conversation with the SECOND person only:
Ask the SECOND caller to hang up or press the hang-up (or Link/Flash) button again.
Helpful Hints:
• If either the FIRST or SECOND person hangs up, your call will not be interrupted. However, if you hang up, the three-way call will end.
• Using Three-Way Calling temporarily disables all Call Waiting features for the duration of the call. Call Waiting is restored once the three-way call ends.