Why am I getting charged more?

There are a few reasons you may have been charged more than more than you were expecting. The first one that comes to mind is that your instance may have exceeded it's Network Transfer Allowance and you were charged for the overage. Each 2GB Linode is allowed 2TB of outbound network transfer per month. If that limit is exceeded, your account is billed at a rate of $0.01/GB (which comes to $10/TB).

You said you kept it on overnight and were billed $75. If the issue was related to network transfer, that means the instance would have used 7TB of network transfer in 1 day, which seems like a lot in a very little amount of time.

Something else that may have happened is that your active plan is larger than the 2GB plan you believe you are using. In some cases folks will have a few different accounts and have different plans running on each.

In any case, the invoice available to you from the billing page in Cloud Manager will have a line-item description of your charges. If you have any other questions regarding the invoice you can always reach out to the Support Team who can give you specific answers regarding your account.