Nice/Nasty😈👿

What is it called when a person is only nice to you when they need you to do something for them???
You rarely speak to one another but when they need you to do something that benefits them all of a sudden they are full of conversation. The tone  in their voice is softer their demeanor is much more pleasant they are all around a nice person verus when they don't need you they are nasty and short with you as if you are a bother to them. 
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Now what if this person is your bf/gfÂ