Realistically, if they're good, you'd have no idea that they're accessing your phone.
There are a couple of ways someone can access your phone.
1. You leave it out while you're in the shower or while you're sleeping. The person accessing your phone knows your PIN and boom, they're in.
2. Remote access via a nefarious app, bluetooth, internet connection, or local network connection. None of these methods are very easy.
Can you define which method you think someone is using to access your phone? What makes you think someone is accessing your phone?
He slips and says stuff he was never told about,we use the same internet access,when I'm talking my phone echoes (my voice).they say to follow your gut and mine is screaming!!!