Google shows contactor as a word but not contacter..
But contactor is a term for an electrical component.
I feel like contacter would be appropriate but I'm not sure. Which would be correct?
I would use a more specific term than contactor. I'd be inclined to use "visitor", if I was contacted in person; "caller" if I was contacted by phone; writer if I was contacted in writing (including in digital media). My reason for not using contacter, is that it is not generally considered an English word, and I believe most readers of English would find it distracting. I would not use "contactor", because while it is a word, it is used so rarely that I would still suspect the reader or hearer would consider it distracting.