I understand that when someone tries to call you, their call is forwarded to a different number. I'm happy to provide some help for this issue.
First, check that you don't have call forwarding enabled on your iPhone:
Call forwarding, call waiting, and other call features on iPhone - Apple Support
Call forwarding Turn on or off in
Settings > Phone.
Contact your carrier for information on using Call Forwarding. To see if call forwarding is turned on, look for this icon in the status bar.
If this is not the case, I recommend contacting your carrier for additional help with this issue. You can find the contact information for many supported carriers in the article below:
Wireless carrier support and features for iPhone in the United States and Canada - Apple Support
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