Oyster maximum/full fare con

So the Oyster card in pre-pay can be useful but their full-fare charging is BAD news - their systems opt to charge you if you mess up at all, and even charge you when don't. The following can incur a full-fare charge:

• Not touching in/out within a station that has multiple gates (e.g. Canary Wharf)
• Touching in and out at the same station straight after one another - e.g. trains are messed up. (in theory you're only charged a 'platform' fee but in practice if the time between touching and out is too short, and/or you're at an open station with one Oyster reader, then you get charged a fullfare).
• Error noise when touching out then trying again (again not always but watch out...)

In any of the above cases call the Oyster help line (0845 330 9876) and then dial 4 (for maximum/full fare inquiries) then ask for a refund - they do usually oblige.