UK Supplier refusing to refund zero rated VAT export to Ireland

Hi all, I was charged UK VAT by a supplier based in England for an export order to Ireland. It’s likely to have been a clerical error on their end and was only noticed by our accountant once we had paid. This has happened before with other suppliers and they offer a refund straight away as exports to Ireland are meant to be zero rated. I’ve sent multiple emails to the supplier with export docs as proof and they haven’t replied in over a month. Sales guy picked up one of my calls and barely uttered two words and said he’d look into it but no response since despite me chasing. The company in question has an annual turnover of +£30m and export to Ireland regularly so I’m pretty sure they know what they’re doing. The refund owed isn't worth going to small claims court over it. Do I have any way to get my money back? FWIW: I'm an Irish VAT registered business not UK registered. Chargeback isn't possible as the transaction has exceeded the 60 days my bank offers. TIA

Hi,
Unfortunately we are unable to offer any help in this matter it is a commercial dispute.
Thank you.