Due to receiving incorrect ticket information from Millwall, advance adult tickets for Tuesday night's game were priced at £15, instead of £10.
Any supporters who were overcharged and have proof of purchase - either in the form or a ticket, receipt or online order - can get in touch with the club for a refund.
Fans can either visit the club shop or call 01438 223223 to arrange a refund.
Apologies for any inconvenience caused.
We are holding a "Drop-In Clinic" on Friday for any supporters who would like to have a one-on-one meeting with regards to the North Stand Mini-Bond scheme. Our team will be on-hand to answer questions and guide you through the investment process.
Find out more by clicking the image below.