context:
1. Driver didn't pick up but has completed my order
We are really sorry to hear what happened. 

Before reporting this incident, if you order GoCar or GoBluebird services, you can try contacting the driver first by sending a chat to the driver up to 2 hours after the order is completed from the Order History page. It's possible that he/she is already on the road to pick you up but accidentally ended the order.

However, if the driver cannot be contacted and does not come after you have waited, you can report this incident to us via Gojek Help page (under My Profile menu) by clicking the Contact Us* button below.

Please note that the driver you report will be sanctioned in accordance with the applicable provisions in Gojek Indonesia and you cannot withdraw your report. So, please make sure that your report is in accordance with what you experienced.
2. Giving star(s) to the driver to rate their service can be done after the order is completed. But, giving a tip to the driver can be done when: 

The order is still ongoing
If you want to tip the driver while the order is ongoing, please go to Orders → Ongoing, then give a tip to the driver by pressing the 'Give a tip' button below the driver's profile information.

The order is already completed
Once the order is already completed, you can tip the driver by go to Orders → History, then select the order you want.

After choosing the order, you can rate the driver by giving a star(s). You also can give a tip* to the driver. *The nominal tip that you can give depends on your GoPay balance.

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based on the context only, answer the following questions. If it's not in context, say I don't know.

1. how to cancel my order?
2. how to file complaint against a driver?
3. driver completed my order falsely - what can I do?