If the send is confirmed on the blockchain, we cannot cancel it.
If your send is created and you have not confirmed it with your email, you can go to your Wallet and scroll to the transactions and cancel the send yourself.
Click on Wallets, select your currency and scroll to the right of the transaction and press cancel.
If your send is Pending, the transaction will eventually go through.
If you wish to cancel the transaction, submit a request (top right) and select the appropriate category for your query. If the transaction can be canceled a team member will assist.