eBay export sales - is it considered as export?

I am an eBay seller doing exports exclusively (100%) via eBay only. I have a VAT & CST Number and IEC. All my customers are on eBay only.  I purchase the goods from my suppliers via Tax Invoice.

My VAT returns are filed ZERO because I have 100% Sales on eBay Only. No local sales within India.

Recently, I have been called by the VAT office to provide proof of exports for 2013 - 2014 and the officers are unable to understand the terms eBay, PayPal, ecommerce etc in Ahmedabad.

I have following proofs that I have sold to foreign buyers:

1. eBay notification of item being sold.
2. PayPal notification of the payment being received from the item that was sold.
3. Notification of PayPal about currency being transferred to my bank account with bank account's last 4 digits displayed.
4. Monthly Invoice from IndiaPost - I use IndiaPost for shipping my products.

The VAT department seems not to be accepting these above as proof of exports. What should I do?

Should I have not applied for VAT and done purchases on Retail Invoices only to avoid this? Should I start making purchases on Retail Invoices from this financial year?

Please help.