[heavy]

That vs Who

This is a gray area but one worth noting, as you'll find these instances frequently occurring. Example:

"The graph on the left represents players that graduated in five years"
You're talking about people, not things...
"The graph on the left represents players who graduated in five years"

Again, this is a gray area. It could be argued either way. Irregardless, I find the latter personifies the customers and clears up any ambiguity (customers are people, not businesses):
"...customers that opened an account..."
"...customers who opened an account..."

Everyone who writes in any capacity should read and have a copy of The Elements of Style by William Strunk Jr and EB White