How to delete my number from the other party's mobile phone?

Impossible, the mobile phone number stored in the mobile phone will not be deleted by external programs. Even if it is deleted, if the address book is backed up, it can still be restored, because most of the address book backups are in the cloud disk, and you can't get in at all.

The only thing you can do is to get the deleted number of the other party's mobile phone and make a backup, so that you can completely eliminate your number.

You can find an excuse to borrow his cell phone and make a phone call to delete it. If you can't meet, buy a new number to call the other party and tell him that the old number is no longer used. You can delete and save the new number.