I signed up for a monthly subscription with the 'renewal' date listed on the invoice. Since this was the only date written there I assumed it was the date which my credits expire so I write down this date to make sure I use all the credits for that month.
Come that day I find that the credits expire the day before (actually at 3am on the 'renewal' day). I send them an email to see if I can still download the images and I get the auto-reply saying I will get a response within 24 hours. One week later, no response, so I email again. Another week and still no reply, so I decide to call them.
I was informed that they can't do anything because of the 'system' but if I pay for another subscription the remaining downloads rollover to the next month if I re-subscribe within the week. Of course 2 weeks had passed since they don't reply to emails so it ended up just being a big waste of money.
This was just the latest incident with iStock, previously they had billed me for 2 months of additional subscriptions even though I had the 'auto-renew' option disabled.