Evolution is only a theory
"Evolution is a theory, not a fact."
This argument relies on equivocation between two meaning of "theory": in common parlance, a theory is an unsupported idea or hunch, e.g., "I have a theory that restaurants make more money off of skinny customers." A scientist would call this a hypothesis or conjecture.
A scientific theory, on the other hand, is a well-supported body of explanations for some aspect of the real world. At its core, "theory" really means "explanation". A hypothesis may become a theory once it has been thoroughly tested through experiment and not been disproved, but will never become a "law" or a "fact", no matter how many tests it passes.
Evolution is both a fact and a theory
Gravity is the force that pushes us toward the Earth. There are also theories of gravity that explain how and why things fall. In this sense, gravity is both a fact and a theory.
Evolution, defined as "allele frequency change in a population over generations" (i.e., populations change over time) is an established fact. Not even Young earth creationists deny that this takes place.
The Theory of Evolution, on the other hand, is a scientific theory that ties together and explains the types of evolution that we see going on, as well as evidence from fossils, genes, proteins, and so on.