You will need the following items for this spell:
a cup of whole milk
1 teaspoon of black pepper
1 teaspoon of horseradish sauce
this might be permanent.
Get a bottle of whole milk, pour it into a cup, no more no less. Next, grab a teaspoon of both pepper and horseradish sauce and mix it. Make it a little warm by warming it up over an open fire or on a stove. Lastly write down the name of the person you want to switch souls with and put it in the drink. Drink it all, and you should feel it work in 4-5 days. These potions take time.
P.S.:
it doesn't matter if the person is unwilling or doesn't know who you are, if the person has a generic name like John Smith, envision their face or photo in your mind really hard, with all your might, also it's best to mediate beforehand.