Apple has done a good job of continually improving Siri to better understand its human overlords, but sometimes we need to step in. It’s actually possible for you to override Siri pronunciations so it both understands and says contact names correctly.
If you’ve got a friend in your contact list with a name like Siobhan, Siri may get the pronunciation wrong. Siobhan can often be misheard as “shuffle”. You can teach Siri the correct pronunciation to better understand it when you ask to call or message that person - ideal if you’re using Apple Watch.
To change the pronunciation simply ask for the contact information of the person by spelling out their name. Siri should bring up the person’s information from that where you can then simply say “Siri, you pronounced it wrong”. You’ll then be asked if it’s the person you’re talking about, tap yes, then you’ll be asked to say the name correctly. Simply do this and then Siri will give some variants of it, that all sound similar to be honest, so you can pick the right one.
Then in future when you ask for anything to do with that contact Siri will better recognise the name and also pronounce it correctly too.
If using Siri to fix Siri seems silly you can also do it via typing. Go into the contact information then down to add field and add the pronunciation section and type in the name phonetically.
This all also works for your name if Siri isn’t addressing you correctly. Simply say “Siri, who am I?”, then after it responds you say, “Siri, you pronounced that wrong”, and go through the correction process that you like best.