I bought a ticket online but can't make it. Do I get a credit I can use it any movie?

Depends who you booked it with, if its Fandango, you can cancel up to 30 min before movie start. With Atom tickets i think its 1 hour before movie start. You can get a refund or exchange it for another movie ticket and/or time

I believe you can exchange it for another time

Not sure call them

I'm sure they'll let you use it another time I'm not positive