Hello Chukwumanj, hope you are having a good day?
Please note that Interswitch makes it a top priority to reverse all failed transactions via any of our platforms. However, we are aware that there are times where you do not get the auto reversal but once this is report (even after months) the transaction is traced and reversed if confirmed failed.
In the case of the transaction you did using your GTB USSD code, please note that the transaction is hosted entirely by the bank and I believe reversals should be done once you inform them.
For security reason, we will appreciate if you could send a contact we can reach you on to consumersupport@interswitchng.com, this is to get details of transactions you might have carried out using Quickteller but did not get value and was debited (this includes the transaction you carried out on Jumia).
Thank you in anticipation.

because they want to do it.