On Wed, 22 Jul 2009 02:06:58 -0700 (PDT), Man at B&Q wrote:

It's an automated system with no intelligence applied. My card was
stopped when I made a purchase approaching £1000 from an on-line
supplier who I've used many times in the past but usually for smaller
amounts.

I've had similar online supplier supllier makes a low value "test"
transaction to check the card details then a few seconds later puts
through the main amount. Trouble is the test transaction orginates in
one country and the main one somewhere else... System spots the
apparent hyper-lightspeed movement of the card and blocks the main
transaction.

Getting the block removed is normally fairly painless, ring 'em up,
tell them the value and with who the last couple transactions where
with and maybe which supermarket and its location you use a lot and
that's it.

--
Cheers
Dave.