We transferred you to our European entity earlier this year, and your IBAN (International Bank Account Number) changed. The old one started with 'GB', the new one starts with 'LT'. This was done to avoid any potential fees imposed by banks on GB customer payments within the EEA after 31 December 2020. There was a coexistence period of two IBANs, but it is ending on 30th September, and only the 'LT' IBAN will be valid.
From this date, if the sender relies on your old account details when initiating a transfer, it will be returned to them automatically and will hit their account within around five days.
You would need to share your updated account details with all of your counterparts, so their top-ups don't get sent back.