Mobile App
1 - Go to (...) More at the bottom of the screen.
2 - Tap Activity.
3 - Tap Repeat at the top
4 - On the Active tab select the automated transaction you want to stop.
5 - Tap 
at the top right corner
6 - Tap Stop repeat transaction
7 - Tap Stop
Web Wallet
1 - In the left menu click Activity, the Widget Panel will show your transactions and, at the top, click the Repeat button
2 - In the Active section click the transaction you want to stop
3 - At the top, click and click Stop repeat transaction
4 - At the bottom, click the Stop red button