I want to turn off my call forwarding bottom but is not working

Call Forwarding, Call Waiting, Call Merge, Conference Call, Hotspot, VoiceMail (Visual or Normal) all are Carrier Specific features. Contact your Carrier (Cellular Service Provider), the agency that issued the SIM / eSIM to you.

Set up call forwarding and call waiting on iPhone

1. Go to Settings > Phone.
2. Tap any of the following: Call Forwarding: appears in the status bar when call forwarding is on. You must be in range of the cellular network when you set iPhone to forward calls, or calls won't be forwarded.

Set up call forwarding and call waiting on iPhone