[You can't prove a negative]
That is a phrase commonly used by many people, even agnostics and especially atheists. First point, if that were true then there is something fundamentally wrong with you and your logic. Why? Because atheists spend an tremendous amount of time and effort desperately trying to prove God doesn't exist.
Secondly, I can show you where that statement goes south. I read a good example recently. If existent is a positive, then nonexistent is a negative. So, you and I can probably easily prove we aren't nonexistent.
Remember, nonexistent is a negative. So, with little effort, we just proved a negative. Of course, getting into a discussion or debate over the existence of nonexistence of God would not be that simple, proving your statement is wrong negates any possible use of it during the debate.