there are 2 different addresses, which one do i write to?

Is it ok to email? or should it done via postal letter? also they said in their email they will collect the £44 on the 1st of july so shall i cancel my dd or leave it?

I am a member of Curtis and Staub, paying a monthly direct debit of £19. The very first payment was taken from my account on the 6/62016. The second was due to be taken on 21/06/2016 for another £19. I did not have sufficient funds in my account. I emailed the gym asking for contact details of harlands and how I should deal with the matter - no response. Each time I went to the gym there was no body on the help desk. I then found their number from a previous email and phoned during my lunch break, I was on hold/waiting for an answer for over 30 minutes both times I called. No answer as I was unable to wait any longer and had to return to work. They have now emailed me saying they need to pay £19 for my membership which I will pay however they have also demanded I pay £25 in administration fee's totalling to £44! I cannot afford this! I am aware this fee is not enforceable! Please could someone advise on how I should handle the matter/respond?