The "price mismatch" message means that an error occurred while trying to calculate the subscription price. In this situation the transaction is immediately cancelled and your credit card does NOT get charged. I've double checked the payment logs to make sure and your credit card definitely has not been charged.
It might interest you to know that the Language Speedway payment system is designed in such a way that if there is ever any kind of system error during credit card processing then the error will always be in the customer's favour. We always renew your subscription first, before attempting to charge your credit card. We then "undo" the renewal only if the credit card charge is declined. If anything goes wrong in this process then your renewal remains valid until we have a chance to investigate the transaction manually. What all this means is that if your subscription has not been extended then you can be assured that your credit card has not been charged.
I had a closer look at the system logs in your particular case and it looks like there might be a bug in the system that can sometimes result in this error if you make a mistake entering in your credit card details. This problem has been logged and it will be fixed as soon as possible. However in the meantime could you please try renewing again, being especially careful to enter all details correctly, and let me know if you get the same error.
I've added a bonus free month to your subscription to make up for any inconvenience. Depending on when you renew you may get additional reminder emails when the extra month is nearly over.
Please let me know if there's anything else I can do.
This bug has now been fixed. You should not get this error again under these same circumstances. If you do, please let us know either in this thread or by email.