Unfortunally we get this question very often and the
Google Market support site has many topics about it.
We would advise you to read the following information on the Google market support site:
Troubleshooting Payments
If you still experience the same problems after taking the steps Google suggests you can contact Google about the declined payment
here.
This is a known issue of the Android Market and there are some large discussions on the Market support site about this.
For more information we advise you to go
here
and let Google know you also suffer from this issue.
No, all our updates on any application in the market are free of charge.
Quoted from the Google Market Support site:
"While it may appear that you've been charged twice for an order, the pending item you noticed on your billing statement is actually an authorization. Authorizations are the initial communication between Google's billing system and the bank's billing system."
If you want to know more about how the charges are handles you can go to
Multiple Charges & Authorizations