I am using `aheadworks iphone theme` in `Magento 1.7.0.0`. But the get a quote or calculate shipping section is not working in first time. 

I have invested the issues and found that when I add product to cart its create two entries in `sales_flat_quote_address` table and then I calculate the shipping by entering `zipcode` in calculating shipping form. 

The old entries deleted which was created during add to cart and it create new entries rather than updating the add to cart entities in sales_flat_quote_address. 

But in case I calculate shipping second time its updating the entries second time.
I am using the core method `checkout/cart/estimatePost`.

Please help me in case you have any idea regarding this issue.

Thanks