Hi,
We have handled this for you. Pesapal e-wallet, visa and MasterCard allow a customer to pay only the value loaded in the iframe [the payment interface],it’s a “pay exactly what you are asked for situation”.
For other payments that use mobile money, a user is required to input the value to pay. If the customer underpays or overpays, the money will be moved from his/her account to our trust account. However, the payment will fail and the merchant will not receive this cash [on the merchant's backend they will be able to see a transaction was made but its status is FAILED]. The cash that has been moved is credited to the customer's e-wallet account [one is created if the customer does not have an account].
For failed transactions, either the customer or the merchant can call pesapal support to have this transaction reversed which is an immediate process.
We have also provided an API that allows your system to query the status of your transactions. Follow the link
developer.pesapal.com/how-to-integrate/api-reference to learn more on how to implement this.
