Need help with extra storage space

Hello,
Last month I purchased an extra 500mb for my gallery. I had the choice of different amounts to add to the free 20mb that came with the forum. I didn't need this much so this month I just opted for an extra 50mb of space and will slowly build up if needed. I waited til this month had elapsed and put in extra 50mb however, I think I have been charged for 550mb. Can someone help me please I only want an extra 50mb not 550mb. This was not clear in the spend summary section. Is there somewhere I can read some more about it?
thanks
CC

I think the option is there for credits to be spent.
50 MB : 50 Credits

Many thanks, In the first month I added 500mg as I didn't know how I would go with the 20mb usage. Now I let that month lapse and went to pay for the next month and only want 50mb but now it says that I have 550mb and charged me 553credits. I feel a bit duped and there is no one to contact except this forum to get it fixed. I have been right through the admin panel and there is nothing. Need help from forumotion credit dept but can't find how to contact anyone
CQ

Well, the best person to help you with this is Typlo. Pm him the details.

Thanks very much, have emailed him now
Karon