I had a similar problem with addresses. I think it was to do with synching. I turned off all synching then went to my main account, Hotmail, and changed, deleted or added so that it was in effect a master copy of my emails and addresses. I then went to every mobile or tablet, cleared all previous email and addresses then turned on synch, and all was updated how I liked it. It is not as long winded as it sounds.
iPhone 7 review: a range of small updates add up to an excellent phone