For a reward-based campaign: yes, but you need to cancel your current contribution and make a new one with the amount or reward you want. This is only possible before the end date shown on the project page.
You will find detailed instructions for canceling your contribution here: Can I cancel my contribution?
Then make a new contribution for the amount of your choice.
Note: if a reward-based campaign fails, or in the event of a refund, you are refunded in full for your contribution, service fees included.
For a donation campaign: this is not possible. Donations are final: they cannot be changed or canceled.
For a subscription campaign: to change your subscription tier or payment method, stop your current subscription and take out a new one. See Can I cancel my contribution? for detailed instructions.