The Bitwala wallet contains a feature called the network fee slider. The network fee slider allows you to manually adjust the Bitcoin network fees associated with your transaction.
To adjust the network fees, simply move the slider on the bar below the transaction details.
Generally, transactions with higher network fees are processed faster by the Bitcoin network. Find more details on the current Bitcoin transaction fees here.
Bitwala does not profit from network fees since they go directly to the miners. There is a set minimum amount of network fees required to ensure that your transaction gets confirmed within a reasonable timeframe.