You can cancel your rental before the first time you unlock the bike, and you will get a full refund. Here's how.
Before your first unlock, you can also change your bike, in case there's something wrong with it. Check in the Rentals section of the app if there are bikes available to switch with form the same pick-up location.
After you unlock your bike for the first time you can switch to a new bike from the same or different pick-up location, provided there is one available. How to switch a bike?
Before your rental period ends, you can extend it! Here's how.
Unfortunately, we can never change the pick-up location or add extra bikes to your rental. But you can cancel your rental before your first unlock and make a new rental with the changes you have in mind.