If you are seeing an insufficient funds error when attempting to send, try sending your transaction again, but first select Send Max Amount. In order to do so, you will need to tap the three dots on the top right of the Slide to Confirm screen and select Send Max Amount.
This button will calculate the maximum amount you can send after mining fees have been included. SatoshiWallet does not make any money from these fees, as 100% of the fee goes to the respective network to pay for confirmations.
In some cases, the network fees may exceed the amount of money in your wallet. This can happen when your wallet contains a large number of very small transactions.