Later problems occurred when ONdigital began to sell prepaid set-top boxes (under the name ONprepaid) from November 1999. This bundle sold in high street stores and supermarkets at a price that included – in theory – the set-top box on loan and the first year's subscription package. These prepaid boxes amounted to 50% of sales in December 1999. Thousands of these packages were also sold at well below retail price on auction sites such as the then-popular QXL. As the call to activate the viewing card did not require any bank details, many ONdigital boxes which were technically on loan were at unverifiable addresses. This was later changed so a customer could not walk away with a box without ONdigital verifying their address. Many customers did not activate the viewing card at all, although where the viewer's address was known, ONdigital would write informing them that they must activate before a certain deadline.