Voiceover Pronunciation Issue

Good morning to all:
I have an issue when trying to change the way words are pronounced in iOS. I have no problem getting the entries done, usually changing the way someone's name is spoken. However, when that person's name becomes a possessive, i.e. an apostrophe s is added, it reverts back to the incorrect way of pronouncing. There is no option I have found to correct words with apostrophes. Anyone have any suggestions? Thanks.