You'll need to make sure all your instalment plans are set to 1 month, which means you'll pay for the entire remaining purchase in-full.
To change any existing instalment plans, you'll need to select the purchase to bring-up the replan screen. You can then move the slider to 1.
Confirm the plan and then repeat for any other transactions you have in instalments.
The remaining amount showing in the app is what you'll need to pay to clear your balance in full.