My wife is manager at Best Buy. Three items in three months shouldn't even alert anyone, unless those three items are identical high value (thousands of dollars) items. Another scenario would be using the store as a "rental service"; you buy a game controller, return it, buy another controller, return it, etc. in other words, you keep buying and returning the same/similar items back to back in order to avoid being stuck with the bill indefinitely.
Not trying to argue or judge based on your returns, but I can say that returning three basic items shouldn't be causing you these issues and I felt that needed to be said so as not to mislead anyone stumbling across this thread.