The following steps will guide you to cancelling a limit order buy:
Go to wallet,
Select the asset you wish to cancel a limit order buy for,
Swipe to 'Open Orders',
Click on the limit order you set,
Click on Cancel Order.

The following steps will guide you to cancelling a limit order buy:
Go to wallet,
Select the asset you wish to cancel a limit order buy for,
Swipe to 'Open Orders',
Click on the limit order you set,
Click on Cancel Order.