It cancels continuous redial read below:
Continuous Redial
This feature frees up your time by redialing busy numbers for you, and ringing to tell you when the line is free.
Service does not work on toll-free numbers, 900 numbers, numbers outside the specified service area, or on a line where call forward and some other call services have been activated.
How to use Continuous Redial:
1. When you hear a busy signal, depress the switchhook and release quickly. (If you've already hung up, pick up the handset and listen for dial tone.)
2. Enter *66 on a touchtone telephone. (1166 on a rotary telephone)
3. If the line is still busy, hang up. Your phone will check the number for up to 30 minutes.
4. A special callback ring alerts you if the line becomes free.(Some phones will ring normally.)
5. Pick up the handset to automatically place the call.
To restart the 30-minute clock; repeat steps 1 – 3.
To Cancel:
1. Depress the switchhook and release.
2. Listen for dial tone.
3. If you've already hung up, lift the handset and listen for dial tone.
4. Enter *86 on a touchtone telephone. (1186 on a rotary telephone)
5. Listen for a confirmation tone or announcement.
6. Hang up.