Late penalty charge - paid on time

Hi, I've been charged this morning £100 in a late penalty fee. I paid the outstanding amount on my account on the 29th Jan, and have the email receipt for this. The 0300 054 5316 number doesn't ring, there's no response at all. Will I be able to get this refunded? Is the best contact method to write given contact numbers don't work, and I can't find email support options. Thanks, 

Hi Paul Bursnall,

Please contact our Self Assessment helpline after 5 working days to review this:

Self Assessment: general enquiries

Thank you.