Apparently, the only way to do this is to completely start a fresh. I am hoping this is not true. Can a number be forgotten by an iPhone so that it won’t appear if a similar number is typed into the phone?
Just a guess here, but can you not tap-and-hold the number in the recent numbers list?
This is easy as you need to go to the "Settings" and select the option for the Call Logs to make changes as you like.