Payjustnow Legit refund system

I purchased goods on the Legit store website got the good need to return some of it at store Level.Went to the store to do refund they can’t assist due to the merchant number that is linked to my account is in letters and they can only do refunds when the merchant number is im numbers. They want issue me with a store gift card but its still my responsibility to pay the payjustnow account